If you're an obsessive Twitter user, you probably notice when someone stops following you. How do you figure out who it is, though? It can be tough, especially if you have a lot of followers. Well, now there's FriendOrFollow, a site that tells you who's not following you back, and who you're not following.

FriendOrFollow is handy for discovering new folks to follow, adding people you might have forgotten, and dropping people (if you're the type to ditch those who don't reciprocate.) FriendOrFollow is a lot like another service that's been around for a whie, Twitter Karma, but it's faster and more reliable. Since there's been more than one attempt to implement this functionality, there must be some kind of demand for it. Perhaps one day you'll see it built into Twitter.