I think the activity that goes on your facebook page is (in most cases) a reflection of how healthy your social life is, and I'm well aware of how pathetic mine is. No one ever writes on my wall, or comments on my (few) pictures. People regularly remove me from their friends (REAL people I actually know).
I really hate it when I stumble onto other people's profiles, and it seems they have an amazing life going for them....hundreds of pictures all over the world, hanging out with different friends, seeing places, and doing things I will never be able to do because I need someone to do them with...
Facebook heavily contributes to my depression sometimes...