I joined Facebook last year, cause friends kept on insisting it was the place to be. I had much grudge against it before joining.
So I use it with many self-restrictions. No photo ever uploaded except profile photo. No stupid application. No friend with people from my parents' generation.
Very little info about myself, and none about my very private life (close friends know it, faraway friends need not to know). No stupid pages of interest except for friends' activities (my former rock band...). No "I like it" !!! Leave a real message instead. Etc.
Result : I use it less and less.
In mind : Diaspora, and other Facebook alikes, which could emerge soon. Pros : your data is your data, on your machine.
Like an enhancement of the spirit of free software in the field of social networking.