I have fun on Facebook, but I check the security settings at least once a week to make sure they haven't changed anything. I keep up with my family there (most of them live in Ohio), and have enjoyed reconnecting with some old friends. One of my high school friends is giving my daughter piano lessons over Skype because of Facebook. It isn't all bad, as long as you're careful.
It does take time to learn where all the settings are, though (including the ones to turn off the posts about all of the games!)