I have an empty FB presence for those times when I need a login. I must operate in some kind of stealth mode because it's pretty bad at knowing anything about me and the suggested matches generally make me laugh. I seem to be going through a Hebrew phase at the moment.
I don't much care what FB/Google/etc. know about me tbh, if they think it's valuable they can have it in exchange for whatever services they provide. I'm smart enough to figure they're not altruistic ventures. Really my life isn't that interesting.
I don't do FB (and social media in general) because I can't be bothered, I'm a grumpy misanthrope, and I really don't want to see pictures of what your kids did last night. I sort of passively like Twitter though even though I'm sure I shouldn't. I have LinkedIn profile though I don't do much with it.
Generally with social media, sort out your identities, remember to assume it's public. The identities thing is a significant one, eople post serious stuff about work, and then here's some pictures of me puking in a bucket on Friday night LOL. Then public, because really it always is.