I'm on facebook all the time. I joined about 3 years ago, and I play games on it and I post pictures and I keep my out of state family up to date with what's going on and I've met my neighbors and have found my friends from High School. I remember years and years ago joining Classmates and found a few people from school but then they started charging and oh, where are they now?!
On the other hand, I lived a full life before Facebook and I reckon I'd be just fine if it went away. I don't pay for any of the services I use on the internet and I won't make an exception for something as silly as having my post on top of someone else's newsfeed! And if one of my friends was doing that on a regular basis, I think I would end up changing their settings or ignoring them altogether!