Sometime today, StumbleUpon will register its five millionth user. (At the time of this writing, it is at 4,994,826 registered users). That number is kind of meaningless, though, because it counts anyone who has ever registered for the Website-rating and discovery service, and who may no longer use it. StumbleUpon, which is part of eBay, does not disclose how many active users it has.

But it did provide me with the nifty little graph above which shows how many times users actually “stumble” something on the Web. (When you like a site or a video you can stumble it by giving it a thumbs up—the more stumbles a page gets, the higher it ranks when others are looking for similar pages). The service is about to collect its five billionth stumble within the next 30 days. Users have already stumbled more than one billion times so far this year. Stumbling activity was up 160 percent during the first quarter of 2008, compared to the same period in 2007 (with 974 million stumbles versus 375 million).

Meanwhile, traffic to the site has been steadily climbing back since taking a huge dive last fall. According to comScore, unique visitors worldwide dropped from 4.8 million last October to 1.8 million in December, but came back up to 3.2 million in March. Many active users never go to the site, and just stumble from their browser toolbar. But as the quality of StumbleUpon’s user-selected index improves, it should attract more casual visitors to its site.

Most people think of StumbleUpon as a socially-powered discovery engine rather than a search engine, but personal discovery and search may be colliding. During a recent speech at the Next Web conference, StumbleUpon founder Garrett Camp noted:

Personalized search is just getting started. I think personalized crawling will start too. Crawlers now are trying to create the biggest map of the web, but implicit filtering and intelligent agents—that is where search and discovery will meet. My query log isn’t actually representative of what I want on the Web.

I like that idea of a personalized Web crawler that indexes only the part of the Web deemed to be most relevant to you and people you know or who share the same interests. Stumbleupon already identifies other users related to you who are drawn to similar Websites, and is building a general index of high-quality sites. The more stumbles it collects, the better its index, and the easier it will be to personalize that down the road. With the number of stumbles rapidly accelerating, the next five billion should take only about another year to gather.

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Now that I have your attention, Compete has released a list of the fastest-growing (and fastest-declining) sites of 2007. Some of the fastest growers include Veoh, LinkedIn, Reddit, StumbleUpon, Six Apart, and WordPress. Some of the notable sinkers are Bolt, Xanga, Netscape, and Autobytel.

TechCrunch has the distinct honor of taking the No. 5 spot in the fastest-growing list, right behind YouPorn and in front of DateHookup. I am not exactly sure what to make of that. I guess Compete thinks we’re hot.

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Subvert And Profit is a service that lets users pay to get their sites on Digg (and more recently StumbleUpon).

Unlike Pay Per Post, the company doesn’t waste a lot of time trying to spin their business into something socially acceptable. People pay them to pollute big social sites and get traffic, and they’re ok with being slammed for that. As long as they make money. The whole operation is complete with founder pseudonyms (Ragnar Danneskjold, Vasili Taleniekov), proxied whois records, and a clandestine PayPal Account.

The service is bringing in the new year with a new pricing model. In ‘08, Diggs and Stumbles will be increased to $2 per vote. Users will be paid $1 for their votes. You can also earn 20% of the earnings of any friends you refer, and 10% of the cost of advertisements from any advertisers you refer.

And they are also expanding into YouTube.

“Crowd Hacking”

Getting articles on the front page of Digg has gotten harder as the community has grown, however. Digg’s algorithms have become more resistant to the same groups of users voting stories, so getting even 50 Diggs is no guarantee of success. Although, S&P claims 9,000 users internationally which they can spread the votes amongst. They also ask users to vote for a random group of other stories to obfuscate their operation. S&P previously claimed a 2/3 success rate.

Assuming it takes 100 votes to ensure a story hits the front page and that it will pull in 10,000 visitors, you’d be paying $0.02 per visitor; a rate comparable to low end remnant advertising. Articles could be much more effective, or not hit at all.

Next Stop, YouTube

While they have not yet revealed how they plan on subverting and profiting from YouTube, we can take some guesses based on Dan Ackerman’s infamous guest post on the subject. Dan’s viral suggestions included email lists, comments, views, blog embeds, and ratings. I imagine S&P’s strategy will center around paying their users to boost each of these.

However, getting big on YouTube is significantly harder than Digg or StumbleUpon. Front page featured videos are chosen by YouTube itself and pushing a video up the ranks in terms of views requires tens of thousands, not hundreds of user actions. I can only imagine their plans include outright view fraud to make the video “go viral”.

Still, I’m left wondering how much all this trouble is worth to advertisers. YouTube videos don’t easily drive traffic to a website, making them harder to audit than referral links from Digg or StumbleUpon. Also, at the end of the day you don’t know how much these services actually contributed to the success of your content. Any statements about the success of these operations come from their founders and are shrouded in promises of secrecy for their clients.

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If you are one of the 3.7 million people who have downloaded the StumbleUpon toolbar to your browser, you may have noticed that whenever a Website that’s been “stumbled” comes up in a Google, Yahoo, or Windows Live search, the StumbleUpon icon and its star ratings appear right beside the link in the results page. (A page that’s been “stumbled” means that a Stumbler found it useful and gave it a Digg-like thumbs up). Now, StumbleUpon is expanding that feature to search results for AOL and Ask, as well as for Google News, Yahoo News, Flickr, Wikipedia, and YouTube. StumbleUpon calls these SearchReviews. In addition to the general star ratings, members will also be able to see whether any of their friends have recommended or reviewed a particular site or page.

“We are doing social search,” says StumbleUpon founder Garrett Camp, “but instead of creating a completely new search engine where you have to change your behavior, you can use the same search engine you use now.” As long as you have the toolbar, StumbleUpon’s ratings get layered on top of other search engine results and Web pages. “We should be able to do this for any site on the Web,” adds Camp.

So why isn’t eBay, which now owns StumbleUpon, one of the sites? The short answer, says Camp, is that it was easier to turn on the other sites first. Making the feature work on eBay would require some custom work, not to mention the temporal nature of its auctions throws a few wrenches into the equation. What’s the point of looking at highly rated auctions that have already expired?

Camp seems more excited about future integration with Skype, which is another eBay-owned client download that sits on many more desktops than StumbleUpon. People who use StumbleUpon like to share their stumbles with their friends, and Skype could offer an instant way to do that. This could be particularly appealing for sharing videos, photos, or music found on the Web. “Skype has that streaming technology that will enable sharing not just of a link,”notes Camp, “but of anything.” This isn’t an announcement, he’s just thinking out loud.

But another added benefit of doing something with Skype would be the ability to import your Skype contacts into StumbleUpon so that you can automatically start sharing with any Skype contact who also happen to be a Stumbler. (Incidentally, you can already do this with Stumbleupon and Facebook, which suggests a partial hack around the general prohibition against importing your friends list into other applications).

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As we expected earlier today, eBay has confirmed an all cash $75 million acquisition of social discovery service StumbleUpon. eBay says StumbleUpon fits will with their “goal of pioneering new communities based on commerce and sustained by trust” and helps them learn more about newly emerging community based businesses.

Although you can imagine “StumbleUpon Shopping” coming soon, eBay is leaving the company alone and taking a wait-and-see approach. The corporation will remain completely intact, except for the addition of eBay’s Michael Buhr, who will serve as general manager for the product.

Throughout 2007, StumbleUpon has seen tremendous growth. They currently have over 2.3 million registered users, serve 5 million daily recommendations, and are experiencing a 150% year over year growth rate. Here’s a quick look at their latest stats from comScore:

More crunch: click here for the StumbleUpon fact sheet.

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I’m hearing that the eBay/StumbleUpon acquisition will be officially announced sometime today - almost certainly at the end of trading. Keep an eye our for the press release. We originally broke this rumor in April when a term sheet was reportedly signed. The Wall Street Journal picked up the story earlier this month.

I don’t know if the price will be disclosed, or if the rumors of $75 million are roughly correct.

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First reported here at TechCrunch on April 18, eBay is now said to be close to finalizing its deal to acquire StumbleUpon for $75 million, according to a new online report from the Wall Street Journal.

The high flying startup has been rumored to be in acquisition talks since November .

The Wall Street Journal report quotes an insider saying that no final agreement has been reached and that talks could still fail.

The StumbleUpon had 2.1 million users as of April, up from 1.7 million in December 2006. 4+ million sites are “stumbled” daily.

The purchase price of $75 million will make a tidy profit for investors who include Ram Shriram and Lotus Development Corp. founder Mitch Kapor: StumbleUpon has only raised $1.5 million in a single round of seed financing previously.

The $75 million is on the high side of our initial range of $40-$75 million. Was there another bidder? Did Google and AOL stake a claim only to be trumped by eBay?

If the deal is finalized it’s an interesting move by eBay. Paypal was core to eBay’s Auction business. Skype could be justified as a tie into the Auction business as well. So where does StumbleUpon sit? People “stumbling” from site to site with a business model the revolves around selling page views seems like an odd fit. A sign that eBay is looking to expand into new markets perhaps? Time will tell.

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This morning we wrote about StumbleUpon’s site specific stumbling and Rafe Needleman’s idea of having a button on blogs that pulls up a random article. I pinged Wordpress founder Matt Mullenweg (TechCrunch runs on Wordpress) after the post and asked him if anyone has created a plugin for Wordpress that does this. They hadn’t, so Matt wrote one and published it.

The plugin is available here. Click here to see a random TechCrunch post from the past, or use the icon in the far right area of the navigation bar above.

If StumbleUpon does decide to offer this functionality as a widget, we’d probably integrate it. The plugin Matt created doesn’t assign any value or ratings to posts. With StumbleUpon, it’s much more likely the random post would be interesting to the reader.

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The most recent StumbleUpon Toolbar (v. 3.05) includes a new feature called StumbleThru, which allows users to stay on a specific web site while stumbling through pages that they might enjoy. Wikipedia, Flickr, MySpace, YouTube, Wordpress, The Onion, and CNN are some of the sites currently enabled (as are the .edu and .gov domain names).

It’s a cool way to find those YouTube videos or Onion articles that will appeal most to you. But I agree with Rafe Needleman - StumbleUpon should release this functionality through an API and let sites include a “Stumble” button. If the reader is a StumbleUpon user, it will take them to a page on the site that they’ll like. If they aren’t, it should take them to a random page on that site and can prompt them to become a StumbleUpon user to get more customized results.

Creating a link to take readers to a random post is a good idea and would only take a couple of minutes to code in WordPress (we’ll do it for fun this afternoon). If StumbleUpon gives away the functionality, my guess is a lot of sites would integrate it to increase page views.

Update: There’s now a Wordpress plugin to generate a random post redirect within the blog. We’ve integrated it. More here.

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On the same day that the news breaks that eBay is acquiring StumbleUpon for $40ish million, Google announces that they are building strikingly similar functionality into their Toolbar. Google (along with AOL) were reportedly in the running to acquire StumbleUpon until very recently.

The Google Toolbar now includes a dice icon. Click it and you’ll be taken to a new website that Google thinks you’ll find interesting based on your previous search queries.

This isn’t an exact duplicate of StumbleUpon functionality, which bases recommendations on your and other StumbleUpon users’ votes of sites. But the end result is the same - serendipitous discovery of new and interesting websites based on your core interests.

Google also has a widget that can be added to their personalized home page with recommended sites.

Om Malik says this is Google lashing out at StumbleUpon and eBay because they lost the deal. Given the timing, I tend to agree.

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