I've never ever used Facebook, and I'm proud of it. I guess we're just two people in my class of 30 who don't have a Facebook account. And you know what? I'm doing just fine. I've never felt the urge to expose my whole life to whoever wants to read what I just bought online or what I'm doing at this exact moment.
Facebook, in my eyes, is nothing but an online networking site with lots of functions, a nice interface and shitty privacy conditions...that went popular beyond belief.
Just try to go a week without logging on to Facebook. I don't know if you can make it if you've first started using it, but you might find that it's really nothing vital to your life.