Flickr rules in photo sharing, as video tiptoes in

— -- Jonathan Racasa of West Covina, Calif., used to share his photos online on Shutterfly, but he wasn't sure anyone was really seeing them. He switched to Yahoo's Flickr and hasn't looked back.

"On Flickr, there's a real community," he says. "You get feedback about your photos, and meet really interesting people."

Racasa isn't the only shutterbug to jump. Yahoo's photo-sharing site has quietly become the most powerful force for dedicated online photo sharing. Yahoo, which is struggling to restore early glory in the face of a bruising, now failed takeover attempt by Microsoft, has a rare hit on its hands with Flickr.

According to market tracker ComScore Media Metrix, Flickr is now the most popular stand-alone photo site. It grew 56% in a year, with 44.4 million visitors worldwide in March, from 28.4 million the previous March.

Flickr is such an integral part of Yahoo, it's one of its most trafficked features, up there with e-mail and instant messaging, says analyst Allen Weiner at researcher Gartner. "Flickr is one of Yahoo's seminal brands," he says.

Unlike e-commerce sites such as Shutterfly and Kodak Gallery, which are designed to sell prints, Flickr is a social network for photo sharing. Pictures are presented larger than at most other free sites, and friends can easily discuss them. Last month, Flickr added video sharing to the mix, in its own unique way. Members can share clips of up to a minute and a half. You must pay $24.95 a year for a "pro" account to upload clips.

Video sites such as YouTube, Vimeo and Veoh don't charge anything to upload clips, and limits are much more liberal. YouTube, for instance, has a 10-minute limit for homemade video clips.

But Flickr had to tread carefully with video so as not to upset legions of photo-sharing purists who didn't want to see the site become a video-sharing site.

The tiny clips are "the kind of video we want on Flickr," says Heather Champ, Flickr's director of community. "We view them as long photos."