For me it's mostly the pictures. There are so many photos of me on facebook in situations (read: drunk off my ass) that I'd simply rather my parents never see.
I stopped regularly using Facebook a couple of years ago. I claim to be one of the first British users, as I was an undergraduate at St Andrews when it first arrived in these shores in 2004. When the floodgates opened, and anyone could join, I knew it's day was up. When I joined it was a genuinely useful tool for keeping track of friends and events at uni, but now it's just an irritant. Even my Dad joined. A passing fad? If only.
I figure if someone wants to murder me, they can do so here randomly. There's no need to learn my identity and stalk me to do it.
Originally, TheFaceBook was just a neat way to stay in touch with friends. There wasn't much talking or other interaction - only messaging, which might as well have been e-mail, and "poking," which was mostly occasional.
I don't think that will happen, but there may very well be a GBook one day, alongside GMail, GWord, all on GOS.
One of my mom's friends joined Facebook and sent her an invitation. Mom has the good sense to ask me whether you should join or not. I told her probably not. And then I told her about this thread.
This is the thing... My mum on it, I can deal with. She tells me everything anyway and I often offer relationship advice. My father blogs about things like his prostate exam being the best experience of his life. I can deal with that. My kid sister posting pics of her getting pissed and sexual exploits. Yeah, I have to ignore her page entirely.