Free advertising. Even if you just get your friends to add your app to try it out - that gets broadcast to all of their friends who look at the news feed (I'd g

Free advertising. Even if you just get your friends to add your app to try it out - that gets broadcast to all of their friends who look at the news feed (I'd guess that few people don't). And if any of their friends are bored and happen to try out your application, then it keeps rippling out. The trick of course, is to build something compelling. The platform will only mature with time, and the really compelling applications - that aren't just profile-based applications, or aren't heavily rooted in a site off of Facebook - haven't been built yet. That's where you come in :)