(1) The doppelganger game: Some of my facebook friends are so absolutely ridiculously conceited and full of themselves. A couple people have transcended the game and been very humorous with this, but those who took it "seriously" failed for the most part, well except for the chicks who are super hawt and actually do look as good as their celebrity counterparts.
(2) The urbandictionary name game: Only because all of them are nearly exactly the same. Don't care that people do it, only that urban dictionary seems to have little originality.
(3) The lack of drunk facebooking: I know there are plenty of facebook friends who drink as much or at least close to as much as I do, and given blackberries, Iphones, etc. its pretty damn easy to do so. Drunk facebooking really should be overtaking drunk dialing and yet its not.