Facebook is basically an imageboard/reddit for people who feel good with their public image and who aren't too controversial.
As far as my experience goes : I'm part of a group mocking anarcho-capitalists there, and it's pretty cool, it's like a /leftypol/ with nice political memes but more diverse opinions and random stuff, and, I don't know, it's kinda like a funny political board except everything get processed by the secret services I guess. At least, my real name isn't there.
Otherwise, I just keep that account to be able to stay in contact with some of my friends who live elsewhere... but I must admit the best friends I have who are far away from me all have my phone number, and conversations between us are way better that way. Most of the interactions I have with old friends I didn't see for more than a couple of years on FB is awkward and end quickly.
At the same time, I don't want to delete my account because I follow some pretty interesting people who do some weird music or art stuff and like to take advantage of the platform, but I kinda hate posting things on my profile. I often get drunk alone and those are the moments when I end up wanting to lurk and post something there. Most of the time, I cringe 20 minutes or the next morning after I've posted something, and change the """privacy""" mode to "only me can see that stuff" option. I guess I have some kind of agoraphobia and self-medicate with alcohol, and Facebook doesn't really help me, except when I gather some likes with a witty remark or a song I post (I actually want to post something from XTC's Skylarking right now).