Flickr has launched its own service - Flickr2Twitter - for sending images to Twitter, and at first glance, it looks like it could compete head-on with existing Twitter photo services like Twitpic and Yfrog. Flickr's system is a bit different than the others, though, and doesn't yet have application support from a major Twitter client. Taking that into consideration, I think there's a good case that these apps will be able to coexist, with Flickr2Twitter dominating amongst existing Flickr users, and Twitpic or Yfrog favored by more casual photographers.

Everyone knows Flickr is a big player in the online photo game, but not everyone has a Flickr account or wants to sign up for one. While existing Flickr users will probably adopt Flickr2Twitter, folks who don't want to sign up can use Twitpic with their existing Twitter logins. Flickr2Twitter also handles uploads via email, so you need to send your photos to your account's email address to post them (the text of the tweet goes in the subject line). For mobile users, this works, but it's not as easy as Twitpic-ing or Yfrogging from your Twitter client, and some of the most popular clients support those services. From the desktop, Flickr2Twitter has the advantage: you can Twitter a Flickr photo very quickly by clicking the "blog this" button that you've probably already noticed on your photo pages.