I joined and provided just the barest amount of information - state, city, a couple of interests - to avoid complaints from friends and family that they weren't sure which [my name] on facebook I was. Didn't want them sending messages to others with my name, thinking it was me. lol
I've never used it beyond that. I don't even accept friend requests.
There are some I wouldn't mind friending, but then it would be taken as rude if I didn't friend someone else.
I also can't remember half the people I went to school with who send requests, and that would get messy.
In general, I'm a very private person, and Facebook is all just TMI in public for my comfort.