If there’s room for one startup in a particular niche on the Web, there’s room for 15 or 20. At least that seems to be the Net’s resurrected credo.

And in some niches, it may even be true. When it comes to online photo storage and community photo sharing, for instance, the burgeoning population of amateur digital photographers is supporting many more sites than might be apparent at first, especially given all the media attention focused on one site: Yahoo’s Flickr. There’s also Bubbleshare, Fotki, Fotolog, Funtigo, Parazz, Phanfare, Photobucket, PhotoShow, PicPix, Picturecloud, Picturetrail, Pixagogo, Riya, Shutterfly, Smugmug, Snapfish, Tabblo, Webshots, and Zooomr, to name a few.

Now the boom in photo sharing has spread to the area of video sharing. New sites have been appearing every month, creating additional outlets and content choices for consumers who are snapping up – and using – increasingly affordable digital camcorders, video-recording cell phones, and portable media players. Most of these sites are free, to boot, and offer members the ability to upload their own digital videos to personal accounts, browse and search other members’ videos, and download video files to hard drives or watch streaming-media versions.

A partial list of new entrants: AOL UnCut Video, blip.tv, Buzznet, CastPost, ClipShack, Dailymotion, Google Video, Jumpcut, Ourmedia, Revver, Streamload, Veoh, VideoEgg, Vimeo, vpod.tv, vSocial, the just-refurbished Yahoo Video, and, most popular, YouTube. And more video sites are in the works, but haven’t officially launched, including Motionbox and Wallop. (Some of these sites also store photos, and vice-versa.)

The boom in “citizen” videography and video publishing arises from both recent technological changes and larger cultural shifts induced by a decade’s exposure to the Internet. “A number of factors came together to unleash the supply and the demand at the same time,” says Jason Zajac, manager of social media at Yahoo, “the mainstreaming of broadband Internet connections, the fact that both professionals and consumers are recording digitally now, the importance of TiVo [which made time-shifting and place-shifting of video consumption easier than ever], and this whole ‘viral’ generation of young people who want to be able to use the Internet to share with the world whatever they think is cool.”

But does this explosion of supply really mean that video sharing has come into its own – and that there is meaningful, compelling content being shared and downloaded? To some extent, the numbers speak for themselves. YouTube, for instance, is the 18th-most-trafficked site on the Web, according to the traffic-monitoring service Alexa. Every day, about three Internet users in every 100 stop there. Not bad, considering that Google, at 27 per 100, reaches only nine times more users.

But traffic statistics don’t necessarily measure the quality of visitors’ experiences. And it’s still difficult for visitors to gauge the differences between, say, YouTube and a Buzznet, Revver, or Vimeo.

The photo-sharing market has had more than five years to evolve, resulting in a variety of sites suited to different consumer needs and tastes. Flickr, for instance, appeals to “alpha geeks” who appreciate the ability to slap comments directly atop photos and label their images with metatags, while a site like Webshots has a county-fair, family-oriented feeling.

But the universe of video sharing is still poorly differentiated. All the sites offer consumers ways to participate in the growing culture of “social media” – the outburst of conversations and communities around user-contributed content, such as photos, videos, podcasts, and blogs. But their features are also largely the same, which was true of most photo-sharing sites back in 1999.

The sites’ content is also similar; at the moment, they all dip into the same vast, heterogeneous pool of amateur, semi-professional, and professional video, from drunken sophomores lip-synching Madonna to Grand Canyon vacation videos to movie trailers and finely crafted film-festival pics. As of this writing, for instance, the top-ranked video on Buzznet was from a concert by the Finnish rock band Apocalyptica; at Yahoo Video, a music video from Reggaeton star Don Omar; and at ClipShack, Episode 4 in a homemade comedy series called “Dustin’s Play Time.”

“It’s a bit like the Wild West,” says Zajac, who led the relaunch of Yahoo’s video-sharing site on May 31. “There is a lot of video from fragmented sources. The quality is all over the map. It’s hard to find stuff that’s good. All we’re trying to create is a service that, for now, makes sense as a place for people to start to experience video on the Web.”

Most video-sharing sites share this catch-all approach, guided not by a clear understanding of what types of videos will prove most popular among Internet users, but by consumers’ own apparent enthusiasm for digitally documenting their lives – and spending voyeuristic hours watching other people’s.

But just as photo-sharing sites have differentiated over time, catering to specific audiences with different sets of features, the video-sharing sites are sure to take on their own individual character. This likely won’t happen along genre lines – after all, there are no photo-sharing sites devoted solely to pictures of flowers or rodeos. Rather, it will happen as the video sites find their core audiences. A video equivalent of Flickr, for example, would appeal to geekier users by providing unlimited storage space for a premium subscription fee, or programming interfaces so that content uploaded to one site could also appear on others, such as blogs. Serious video filmmakers, meanwhile, might gravitate to sites that offer members personal “channels” showcasing their own work (a feature added to YouTube last week). Lower-end sites would likely remain free and advertising supported, relying solely on the “funniest home videos” flavor of much amateur content to keep traffic flowing.

But, until then, video-sharing sites are more like fire hoses than drinking fountains. “The world’s changing,” says Anthony Batt, CEO of Buzznet, which markets itself primarily as a community gallery for member videos of pop-culture events such as rock concerts. “We are giving these people phones and cameras to record with and the Web tools to infinitely broadcast what they record. We are in a sea change – and helping that to occur is the exciting thing about this. We want people to take photos of their lives and their surroundings and share it immediately.”