I have been on facebook for a few weeks now. I am not certain if I think it is a useful forum or not for life.
What seems to be good is that is a convenient and quick way to share your photos. You also can find long lost friends, but beyond that, what it is good for I am not sure.
I have a moderate list of friends on there.
Laika has her own Dogbook page. Fun, but not really useful.
Facebook seems to be oriented to people in their late teens and early 20s, or at least that seems to be who uses it.
I will keep myself on there and report back if I think there is anything earth shatteringly useful from the site.