I've been on FB about 4 years now, since my 20th HS reunion. It's fun, mostly use it stay to connected w/ people I've known in real life over the years (hs, college, grad school, various jobs, etc). Some people take it way too seriously and spend way too much time there, but that's an issue w/ social networking in general.
It's a great site for photos..I've enjoyed a variety of racing photo galleries, and pages like Motorsport Retro, the pages for various magazines, etc..