Alex Kates writes that Facebook applications suck because the only really popular ones are 1) awful, and 2) viral.
We use 'viral' too often to remember that it's not necessarily a good thing. A 'viral' video is, obviously, a video that people see and want to forward to their friends, who see it and want to forward it, etc. But any virus will slough off features that aren't necessary to getting passed on -- which is what has happened to viral Facebook apps. They aren't 'viral' anything -- they're just pure viruses. The most common I've seen are 'vampire', 'zombie,' and 'werewolf' applications, with which a user 1) adds the application, and 2) tries to get other users to add it, too. It's okay that these things exist, even if they're bothersome to ignore, but I'm going to request some honesty:
Someone needs to create a Facebook AIDS application. Add it, and you're Facebook-AIDS positive! Try to infect all of your friends!