They may be mysterious and perhaps even a bit shady, but secondary equity markets, which allow employees to sell off their shares to other buyers, are quickly heating up. Because of the rarity of IPOs and acquisitions in the startup world these days, early employees and founders are becoming increasingly anxious to convert some of their shares into cash (one need look no further than reports of employees selling Facebook stock at relatively low prices for proof).

Unfortunately, because these markets are trading shares of private companies, buyers and sellers are often left in the dark as to the worth of their stock. SharesPost, a private equity market that’s currently operating in public beta, is looking to help: the site has launched a publication platform for analyst reports meant to complement its equity market. And it’s offering a free two month membership to TechCrunch readers, which you can sign up for here.

As a teaser for what’s available on the platform, the site has shared two valuation reports on some of the world’s biggest social networks: Facebook and LinkedIn. You’ll want to check out the full reports here and here to read the full analysis and methodology (you may have to register).

LinkedIn has bolstered its position as America’s leading business social network by the month lately, with Germany-based Xing as the only company regarding itself a worthy competitor in the last few years. But now those days seem to be over - in the US and China, at least.

Today German newspaper Hamburger Abendblatt published an interview [GER] with Xing CEO Stefan Groß-Selbeck (who recently replaced founder Lars Hinrichs), and he revealed a couple of interesting tidbits of information about the future direction of his company (find a horrible, Google-translated version of the full interview in English here).

Talking in broad strokes, Groß-Selbeck said 3.5 million of the 7.5 million Xing members are based out of Germany, Austria and German-speaking Switzerland. This isn’t really that surprising, given the background of the company. But the interview also marks the first time a Xing representative publicly (albeit indirectly) admitted losing in the USA and China.

LinkedIn had a management shakeup last December - CEO Dan Nye stepped down. Founding CEO Reid Hoffman stepped in again and former Yahoo exec Jeff Weiner joined the company as President.

The hiring of Weiner as President was clearly an interim move, and we predicted he’d move into the CEO role sometime this year: “The addition of Weiner is also quirky, and may explain the changes. Weiner was likely expecting a CEO role as his next job. He’s now second to Hoffman. Perhaps the company is using the interim period to see how he can handle himself leading the company. I wouldn’t be surprised to see Weiner take the CEO job at LinkedIn sometime in 2009, or else leave the company.” It turns out that is exactly what happened.

LinkedIn continues to roll. They are the fifth most valuable social network according to our recent model. The site attracts over 15 million monthly unique visitors (Comscore worldwide, April 2009), up from less than 7 million a year ago, and has 42 million registered profiles. They’ve been ebitda profitable since last year and say they plan to be cash flow positive this year. In February, Hoffman told me “We can go public any time we want to.”

And Weiner agrees, telling me today that their current plan to to build an independent public company, with three key revenue sources: premium subscriptions, corporate solutions and advertising. To date the company has raised over $100 million. The last round, a year ago, valued the company at just over $1 billion.

It’s ‘official’; big shot CEOs are social media slackers. The hot news comes straight from ÜBERCEO, who says it conducted research on the topic for the past few weeks and has found that there’s little chance you’ll ever get to exchange pokes and tweets with Fortune 100 CEOs for the time being. Here’s the ‘miserable level of engagement’ ÜBERCEO has uncovered:

(after the jump)

Industry white papers, in general, are dull reading—unless you need a piece of information in one of them to do your job. Then you’ll pay almost anything (i.e. expense it) to get your hands on the white paper you need. Sometimes companies produce white papers and give them away for free, but they have a hard time finding the professionals who might be interested in whatever narrow topic the paper covers.

Enter LinkedIn. It knows what industry you work in and your job title, making it easy to guess what kinds of white papers you might actually be interested in. The business networking site is testing a new feature that turns white papers into ads and presents them to the narrow group of professionals most likely to want to read them. LinkedIn members can get white papers for free, and in return sponsors get qualified leads.

A year ago we modeled out the true value of various social networks based on the idea that users in high-value online advertising markets like Japan, the UK and the U.S. were worth more (financially speaking) than those in lower value online advertising markets. Facebook had recently become the largest worldwide social network in terms of users, but based on our model MySpace was still by far the most valuable social network.

We’ve now remodeled social network valuations based on current user numbers and Facebook’s most recent $10 billion valuation. The results are dramatically different.

Based on the original year-old model, if Facebook was worth $15 billion (their then-current valuation), MySpace, with far more U.S. users, was worth nearly $20 billion:

Our model takes Comscore data for available countries and regions. We’ve graphed each of 26 well known social networks with the data we have been able to collect. We’ve then calculated the average advertising spend (estimated by PriceWaterhouseCoopers in a recent report) for each person online in each of those countries. For example, in the U.S., the total 2008 estimated Internet advertising spend is $25.2 billion. We’ve divided that by the number of people online in the U.S. according to Comscore (191 million), to get an average Internet spend per person of $132. View the raw data and calculations here.

The U.S., by the way, is only the 4th most valuable market per Internet user, trailing The UK ($213), Australia ($148) and Denmark ($144).

How quickly they grow. Remember when Twitter was just a little pipsqueek, with less than 10 million monthly unique visitors to its site worldwide? That was back in February, 2009. Fast-forward to April, and Twitter’s U.S. visitors alone reached 17 million. Now comScore has released its worldwide numbers and it estimates Twitter’s global unique visitors in April, 2009 was a whopping 32 million, up from 19 million in March, 2009.

To put that in growth into perspective, Twitter has just passed Digg (23 million), LinkedIn (16 million), and the NYTimes.com (17.5 million) in monthly unique visitors, as counted by comScore. And comScore only measures the number of people who visit Twitter’s Website, not the millions more who send and read tweets via their phones, desktop apps, or other Websites. Twitter.com is also now bigger than Bebo and Freindster, for what it is worth. Who will it pass next?

Facebook, MySpace, LinkedIn, Yahoo and now Google. What do these have in common? If you’re reading this blog, you probably have a profile on all of them. And those are just the obvious ones, you probably have a bunch of other profiles on a series of other networks too. The situation has become untenable.

Imagine if you wanted to update one piece of information on all of them — like I recently had to do with a job change. That’s a lot of work for such a minor tweak. But if you don’t do it across the board, there will be incorrect information about you out there on the web. Information that is always just a search away.

The guest post below was written by Reid Hoffman, CEO and Founder of LinkedIn. Reid, who’s been a prolific writer lately, is a strong advocate of entrepreneurism and the startup mentality. See his recent Washington Post article Let Our Start-Ups Bail Us Out, and the guest post he wrote here on TechCrunch, Stimulus 2.0: It’s The Startups, Stupid. Reid has recently appeared on Charlie Rose, and we had a chance to sit down with him earlier this year for a video interview as well. Reid is an investor in over 60 web ventures including Digg, Facebook, Flickr, Friendster, FunnyOrDie, Ning, Last.fm, Six Apart and Technorati. He is also a member of the nominating committee of our upcoming TechFellow Awards with Founders Fund.

TechCrunch and Founders Fund announced the first annual TechFellow Awards last week. This is a great time to stimulate investment and recognize and encourage tech entrepreneurs –starting up is cheaper, talent is more fluid, and people are more inclined to take calculated risks. If we can find more ways to spur investment, it will be good for the entrepreneur now and good for society later.

As a serial investor, I’ve enjoyed backing some good Web 2.0 companies, and it’s helped me develop a shortlist of criteria to cut the wheat from the chaff. After five minutes of a pitch, I know if I’m not going to invest, and after 30 minutes to an hour, I generally know if I will. Many entrepreneurs are product-focused, which leads them to pitch the brilliance of the product. Others are money-minded, so they can over think the business plan. But neither of these approaches answer the first few questions I want to know as an investor:

Managing Groups in LinkedIn so far didn’t require a whole lot of management, nor was it very useful to those who created them. While other social networking services have long incorporated ways for group administrators to communicate more efficiently with their members, LinkedIn for whatever obscure reason never even bothered to create a feature that allowed admins to e-mail group members directly for the sake of sharing announcements.

I got an e-mail from LinkedIn just now letting me know that this feature is now finally being added, “in response to overwhelming demand from group managers” (no kidding) and that group managers can now blast out e-mails with announcements and create a discussion topic that members can comment on automatically in the process. As a privacy measure, LinkedIn is removing the ability to download or view member e-mail addresses.

uTest, a startup that allows companies to outsource their QA testing to ‘the cloud’ has just concluded its latest quarterly bug battle, during which it put some of the world’s largest social networks to the test. Hundreds of participants (many of which have been involved in product testing for over a year) did their best to uncover flaws across Facebook, MySpace, and LinkedIn, with $3,000 up for grabs for the testers who identified the most crucial bugs.

Below are the final results for the number of bugs found. It’s worth noting that this data is prone to bias and may well overstate the number of ’showstopping bugs’ (testers probably had a strong incentive to rate their bugs as ’showstopper’ so as to have a better chance at the prize). But it also meshes fairly well with anecdotal experience.

Angel and VC funding platform Angelsoft has launched an investor filtering tool, allowing entrepreneurs the ability to access detailed profiles on over 1,000 venture capital firms and angel investment groups in the U.S. Angelsoft allows startups to “push” their business ideas to over 400 angel investment groups and 15,949 investors across the world. The site formerly focused on connecting entrepreneurs to angel and early-stage investors only, but recently changed its model to include VC firms.

Angelsoft calls it an investor search engine, but it lacks a search box (a big flaw). Instead, entrepreneurs use Kayak-like filters to adjust their sorting results by how much an investment firm usually invests, what terms they typically offer, as well as by company-based criteria such as industry, location and stage. VC and angel firm profiles include a snapshot of the fund, industry expertise, prior investments, executive profiles and links to the LinkedIn profiles of investors. For the 450 investment groups that use Angelsoft’s VC and Angel dealflow management tools, the search engine results provide even more data, including a firm’s average response time to entrepreneurs applying for funding, number of applications a firm receives each month and additional past funding history.

Reid Hoffman is an entrepreneur’s entrepreneur. He worked at Paypal, founded LinkedIn, and invested in dozens more. Last night, he appeared on Charlie Rose, where he talks about the rise of social networking in general, and LinkedIn’s success in particular (it is adding one million professionals every 17 days and is emerging as a “low cost provider of really good hiring services”).

Yesterday, Hoffman wrote a post for us with some concrete suggestions for a Stimulus 2.0 plan led by startups. He hit some of the same themes on Charlie Rose. The best part of the hour-long interview, however is towards the end where Hoffman discusses the role that entrepreneurship can play in getting America out of its rut.

(Video, excerpts, and full transcript after the jump).

Editor’s note: The guest post below was written by Reid Hoffman, CEO and Founder of LinkedIn. Reid has some strong opinions about how startups can help right the economy, and he offers some suggestions below. (You can also catch him tonight on Charlie Rose, or check out our interview we did with him at Davos). Reid is an investor in over 60 web ventures including Digg, Facebook, Flickr, Friendster, FunnyOrDie, Ning, Last.fm, Six Apart and Technorati.

While at Davos this year, the conversation spurred a lot of thought about how we can navigate through the economic crisis. Yesterday, I shared a few of these thoughts in a Washington Post op-ed to offer a Silicon Valley perspective to lawmakers.

I believe the real fix for the economy is massive entrepreneurship and innovation to create new jobs through new products and services. Here are a few of my proposals:

As layoffs continued to pound the economy in January, one beneficiary was job networking site LinkedIn. According to the latest January data from comScore, the LinkedIn’s U.S. unique visitors shot up 22 percent to 7.7 million, up from 6.3 million in December. Total minutes spent on the site doubled in January to 96.8 million, from 47.6 million in December.

Part of what is driving all the activity is people looking for job, and helping friends who are out of work. Recommendations are up 65 percent since December, says spokesperson Kay Luo. LinkedIn’s improved people search, which it launched at the end of November, is also driving a lot of activity on the site. The company is seeing a 50 percent increase in activity on the new search platform.

When times are tough, networking is a survival skill.

LinkedIn may be profitable and growing fast, but something seems to be going very wrong with the business social networking service today. The service has been going up and down all day over here in Europe, and has now been displaying an ‘Oops’ page for the past 55 minutes (4:30 PM CET).

Update: it’s back up, downtime lasted exactly one hour.

Update 2: and it’s back down again (4:45 PM CET), they’re having serious technical issues over there.

Update 3: it’s bouncing up and down. Seems to be stable now (4:52 PM CET)

It’s a very unusual thing to happen with LinkedIn, which has always had quite a reliable web service, and there’s no official update to be found on the LinkedIn Blog (which is still up). Meanwhile, Twitter users are spreading the word about its current downtime fast.

Update 4: The problem was to many backed up messages, specifically LinkedIn’s Message Queuing. Explantion is up on the LinkedIn Blog.

Next up in my series of interviews recorded at the World Economic Forum in Davos, Switzerland last week is Reid Hoffman, the founder and CEO of LinkedIn. I spoke to Reid for more than twenty minutes in the lobby of our hotel about a wide range of subjects, including LinkedIn’s product plans, fundraising activities and revenue.

LinkedIn has raised over $100 million in financing - roughly $75 million of that was in 2008 alone. The company has been profitable for the last two years, Reid says, and has $80 million in the bank.

I spoke with Reid at length about whether he’d consider a merger with Facebook (he’s buddies with most of the Facebook execs that attended Davos and was spending a lot of time with them). His flat out answer is “no,” there aren’t any discussions going on with them. And he insists that personal and professional networks shouldn’t be linked. At the very least they need to stay separate brands, he says.

Meanwhile, LinkedIn continues to grow like a weed, adding a million new registered users every seventeen days. With that $80 million in the bank and 2 years of profitability, he’s not being unreasonable when he says, near the end of the interview, “We’ve been profitable for the last two years, so when we want to IPO we can do that.”

The full transcript is below.

The World Economic Forum in Davos is finally trying to make its mark in social media at this year’s conference. The organization is unveiling the beta version of its exclusive Facebook-style social networking site, called WELCOM, reserved for high-profile attendees of the World Economic Forum like Mark Zuckerberg, Vladimir Putin and Kofi Annan.

The site, which was designed in partnership with Adobe Systems, BT Innovate and Microsoft, will actually be a pretty nifty way to share ideas between the world’s best and brightest. That is, if world leaders will bother to take the time to contribute to the site and establish profiles. (Don’t count on it).

LinkedIn has partnered with IBM to create a new plugin that integrates its professional social network into Lotus Notes, a popular business desktop client that includes Email, calendar, and IM functionality. The plugin is making its debut to the public at Lotusphere, with plans for its release in the first half of 2009.

For users who spend much of their day ‘living’ in their Email client, the new plugin could be a welcome addition. Its primary purpose is to display information relevant to the people in your Emails, as well as providing a handy way to browse through some of LinkedIn’s most oft-used features (like your news feed and search). However, the plugin does not yet automatically look up the contacts mentioned in your Emails - you’ll still have to click on their names or use the pre-populated search to look them up (automatic lookup is planned for a future release).

Year end Comscore numbers for the U.S. audience are out. The first thing we checked? How the major social networks are doing.

Facebook, which became the largest worldwide social network in mid 2008, is still playing catch up to MySpace in the U.S. They have 54.5 million monthly unique visitors, says Comscore, compared to nearly 76 million for MySpace. But Facebook’s growth rate in the U.S. averaged 3.8% per month over the last twelve months. MySpace’s U.S. growth rate is 0.8% per month. That’s nothing to be ashamed of, but unless things change a lot, Facebook will overtake MySpace to become the largest social network in the U.S. in…2010.

At current growth rates Facebook will overtake MySpace in January 2010, a year from now. That is the month Facebook will reach 86 million U.S. users, compared to MySpace’s 84 million in January. Will this prediction be correct? Probably not, but it’s the best guess given today’s data.

It may actually take longer. Facebook’s growth rate had been increasing as the year wore on but dipped in December. As they get closer to MySpace it may become ever harder to catch up.