I barely write on my Wall and have no pictures up. Facebook has let me reconnect with a couple of college friends, but basically I use it to see what my friends in AZ are up to. I've vicariously seen quite a few of my older son's friends and classmates from first grade because of a circuitous connection between one of my "friends" and them.
I could sign off today and it would make no difference to me. As far as Twitter, it seems extremely egocentric. Even my 20 something kids think it's useless.