Photo-sharing on the Web keeps getting more popular as people transfer more of their digital photos from their the black holes of their computer hard drives to social networks where their friends and family can actually see them. Although Facebook Photos has emerged as the largest photo-sharing service in terms of users and is one of the fastest-growing of any size, it is still not the largest by the sheer number of images that it stores.

That honor, for the moment, goes to ImageShack, which currently hosts 20 billion images, I’ve confirmed with the company (for more background on ImageShack, read this post). Facebook holds 15 billion photos, according to a spokesperson there. But it should catch up by the end of the year. Facebook users are adding photos at a rate of 850 million photos a month, compared to 100 million photos a month by ImageShack users. Good thing Facebook just fixed its storage architecture to be able to handle the bigger load.

Heres an idea: If you’re looking to build up your social site’s user base, add support for a popular, similarly focused (but not directly competitive) social site to your network’s iPhone application. It may sound crazy (who wants to promote someone else’s brand?), but that’s exactly what Radar, a social network for sharing cameraphone images and videos, is doing. This morning, Radar has released an update to their iPhone application which adds Flickr support to the mix.

Though Radar and Flickr are quite similar in that they’re both intended as repositories for your photographs, their finer focus differs just enough for this idea to work. Flickr is generally used for collections of high resolution images, with the comments area serving as a grounds for conversations that stretch on indefinitely. Radar, on the other hand, is more for spur-of-the-moment, heres-what-I’m-doing-right-now type stuff.

If Facebook has one standout application it has to be Photos. Measured on its own, it is the largest photo site on the Web. A full 69 percent of Facebook’s monthly visitors worldwide either look at or upload photos, based on comScore data. And more than 10 billion photos have been uploaded to the site.

And it’s been pulling away from its competitors. As can be seen in the comScore chart above, as recently as last September the top three photo sites in the U.S. were running neck-and-neck, with Facebook Photos at 23.9 million unique visitors, followed by Photobucket at 21.3 million uniques, and Flickr at 19.5 million uniques. But by January, the number of monthly U.S. visitors going to Facebook Photos shot up 41 percent to 33.6 million. Meanwhile, Photobucket is up only 7 percent to 22.8 million, while Flickr is up 12 percent to 21.9 million. (Picasa is a distant fourth in the U.S. with 8.1 million).

In other words, Facebook increased the gap between its closest competitor (Photobucket in the U.S.) from 2.6 million monthly unique visitors to 10.8 million. On a worldwide basis, the gap between Facebook Photos and Flickr (which is the No. 2 site globally, and looks like it is about to pass Photobucket in the U.S.) went from 41.2 million unique monthly visitors in September to 87 million in December (the most recent data available, see chart below).

What accounts for Facebook’s advantage in the photo department?

Everyone knows there are lots of amateur and hobbyist photographers out there, and collectively they produce a massive amount of material stored on online photo sharing sites and desktops around the globe which might just contain that one image an advertiser was looking to use to communicate a message.

Adography is a relatively new service that offers a way to monetize your own amateur photos if you think there are some who might make for great advertisement material.

Adography is essentially a marketplace where people can put their amateur photos up for sale, while businesses can put out requests for photos by creating so-called ‘want-ads’.

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).

MyFolio is a brand new social network in public beta that takes another crack at building an online community service for artists and creatives looking to share their art and converse about it with like-minded people. The startup quietly launched the website a month ago and is entirely bootstrapped by its founder Mustafa Lazkani.

In terms of features, MyFolio covers every basic need for a social network to be useful for its creative audience. Artists can upload and tag media or files for a variety of categories ranging from animation, concept art, films, paintings to music and photography, create a portfolio, manage bookmarks and keep on top of internal messages from other users. Registered users can indicate of their work can be viewed in public or kept private, if it is work in progress or not, and which copyright applies to the work.

Yahoo needs all the revenue help it can get these days, which is why it’s odd that subsidiary Flickr hasn’t been serving ads properly for a day or so and apparently no one at the company has noticed. A reader writes in to point out that if you click on any of the ads that appear on the site when you do a search (try this one for Apple), the user sees the linked page in an iframe instead of being taken to the advertisers site.

That’s handy, because the advertiser is charged but the user never leaves the Flickr site (something only Facebook seems able to pull off). My guess is this is fixed by morning.

A U.S. Airways plane leaving New York City crashed in the Hudson River a few hours ago, possibly due to a bird striking the engine. Rescue operations are under way. Apparently all passengers are safely off the plane now. But I’ll tell you one thing: it’s freezing in New York City today. I can only imagine what it must have been like on the water.

Pictures of the plane floating in the river are already on Flickr, Tumblr, and TwitPic (which seems to be overloaded right now). In fact, the picture above was taken by Janis Krums who Twittered it from his iPhone, and posted via TwitPic.

In late 2007 Flickr was strongly considering creating a marketplace where users could buy and sell photographs hosted on the service. It was to be called Flickr Stock.

Then-employee Sarah Cooper worked on the project and describes (Update: it has now been removed) it as “The concept of Flickr Stock was to create an online marketplace where existing Flickr users could offer photos for sale as well as purchase photos taken by others.” Cooper worked on the project in late 2007. She also published the screen shots included in this post.

Flickr Stock would have let any Flickr user sell their photos to others, something more than a few people think is a good idea.

But Flickr abandoned the idea in early 2008 and decided instead to partner with Getty Images. A just launched beta program lets a handful of Flickr photographers sell their images on the Getty Images website. That program is being expanded and should launch in the next couple of months, Flickr General Manager Kakul Srivastava told me this afternoon.

JPG magazine, which was declared dead less than a week ago, is most definitely for sale and it looks like a transaction will close shortly.

Twenty or so potential buyers have expressed interest, say our sources, including Flickr (a natural fit because the photos published by JPG Magazine are submitted by readers), Smugmug and Alexander Muse. Wordpress also expressed early interest, we’ve heard, although they’ve pulled out of the bidding.

It’s unclear how much it’ll take to get the JPG Magazine assets, but our understanding is that 8020 Media, the company behind the publication, is fielding cash offers only and is being fairly successful in getting a bidding war going.

What were the top social media sites of 2008? ComScore came out with its worldwide traffic stats for November a few days ago (so these don’t include December). They are a mix of social networks and blogging platforms. Blogger, the orange line in the chart above, still rules the roost with an estimated 222 million unique worldwide visitors in November (up 44 percent from November, 2007). Facebook, the blue line, is on pace to pass it soon with 200 million unique visitors (up 116 percent). (Note, though, that this is more than the 140 million active users Facebook itself reports—go figure). MySpace is pretty steady at 126 million uniques. Wordpress is a close fourth and gaining with 114 million (up 68 percent). And Windows Live Spaces is down 22 percent to 87 million uniques.

ComScore keeps a list of what it calls “social networking” sites, but these include blogging platforms and other social media sites as well. While the audience for blogs is still showing healthy growth overall, Facebook stands out as the social gorilla taking share from not only other social networks but blogs and other social media as well. Below are the top 20 sites on comScore’s social networking list.

Forget CNN, which so far has few details of the ongoing attacks in Mumbai, India that have left at least 80 dead (Update: they’re starting to catch up now). People are giving first hand reports of what they’re seeing directly on Twitter. Flickr is another important information resources – images are here.

Twitter isn’t the place for solid facts yet – the situation is way too disorganized. But it’s where the news is breaking. GroundReport is doing a good job of aggregating citizen reports. Both Wikipedia and Mahalo have constantly updated pages with known facts.

We all know how tagging makes the Web a richer place (by tapping into people’s desire to categorize things and share those categories, ad-hoc though they may be, with the everyone else). Tagging brings a bottoms-up order to the Web by making information more searchable and thus easier to find. Now it is time to start tagging the world. The real world.

In fact, millions of people are already doing so every time they upload a geo-coded photo to Flickr, add a review to Yelp, Tweet about a specific place, or use any of the dozens of geo-aware social apps springing up all over the place. They are not just tagging the world with keywords, they are commenting on it and annotating it in tiny little bursts.

Geo-coded communications are becoming more and more common, and this is just the start. I like to complain about the increased noise level that lifestreaming services are bringing into our lives. While that continues to be a growing problem on an individual basis for people who want to tune in and use these services (”You’re at the bus stop? Great. Keep those Tweets coming.”), on an aggregate level all the seemingly useless drivel has the potential to become useful meta-data.

A Flickr user named Garrett Ryan Smith uploaded the 3 billionth photo to the site today. The last big milestone was 2 billion photos, a year ago.

They’re well behind Facebook, with 10 billion. And they’re falling further behind – a year ago Facebook had just 4.1 billion photos.

Still, it’s a staggering number of photos for a site that launched in 2004.

This picture was presented by Elizabeth Churchill, Principal Research Scientist at Yahoo at a meeting I am attending today. It shows the privacy settings of a sample of a million Flickr users from 2005. Red spots note users who have photo sharing turned off (private), green shows users who have photo sharing turned on (public).

The results are fascinating. The US is widely public except for users who seem to be hovering around Utah, and varies by state. Europe, by contrast, is largely private, and more so as you move north. The Middle East is wide open. South East Asia is mixed. India is private.

On the heels of a major upgrade earlier this week that added facial recognition and video-editing features to its Picasa photo management service, Google added a new Explore page today that shows off the most popular public photos uploaded by members. In addition to the featured photos, shown in a 3 X 4 grid, the Explore page also shows the most recent photos uploaded in a slide-show widget. Below, it offers a list of the most popular tags. For instance, here are pictures tagged “New York.”

The Picasa Explore page also has a Where In The World? game that is mashup opf geotagged photos and Google Maps. It shows you a photo and you have to guess where it was taken. If you guess wrong, it tells you how far off you are in kilometers. This is fun for outdoor photos, but when people upload geotagged photos of a generic apartment of a plate of food, it can become tricky.