Facebook is wildly popular. Almost everyone I know has one, and it's really convenient if you have relatives who live far away. But there are many privacy issues with it. It's not safe to post anything there, really. If you are fine with everyone knowing your business, then FB is the site for you.
Another problem with this site is that people in general are annoying. There are the over sharers, who tell about every single thing they do every day. Then there are people who post a constant flood of memes. Don't forget the people who post vague stabs at "unknown" people who have apparently wronged them.
I am also sick of seeing "If you don't share this, you worship Satan" type things.
I'm sorry but FB is NOT great. As I mentioned before, it may be convenient to talk to family members you never see, but I don't know if it's worth all the irritation. Why not just call your family?