Digital photography can be thrillingly addictive, as the online phenomenon known as Flickr makes clear. Flickr isn’t just your typical, run-of-the-mill spot for storing your photos and having prints made from them. Flickr is about sharing your images, and tagging them, and maybe even developing friendships around your photographic obsessions, whether it’s photos of squares within circles, say, or Polaroid-looking images, or iPhoneography. Flickr is something of a subculture, or set of subcultures. Whatever your photographic interests, you will find communities of likeminded photogs eager to gather online. And the more you use Flickr, uploading your images to your “photostream,” the more addictive it becomes—even spawning fun, diverting offshoots in the form of games and whatnot.