As an army brat and such, I have moved often, and FB allows me to keep in touch with practically everyone. I also come from a big family, some I have never met, but we have friended on FB and thus become a part of each other's lives.
My mother also uses it to keep an eye on me
I enjoy posting pictures from my phone, and gets lots of feedback when I need it. Even my grandfather is on FB - and actively uses it!