I like facebook and it's a great way to share photos/events/stories with overseas family and friends. Like a more personlised interactive forum haha.
I wanted to look up all my old high school friends and facebook was awesome for reconnecting. "oldfriends" site just didn't cut it. Now we're organising a reunion - fantastic!
My teens use facebook and as a parent it's a very interesting look into their world!
The biggest issue is security and you've just got to keep on top of it, make sure all your settings are how you want them, (eg friends only) and be on the watch for facebook scams and hoaxes. I regularly check http://www.facecrooks.com/ if something looks suss and I have a regular cleanout of applications that haven't been used in over 6 months.