I don't see the point, either. That's why I've so far refused all the "invitations" to join MySpace, Facebook and BeBo.
I do have a Flickr account, but I use that to upload photos that I want to share via the Internet (sometimes I have too many to email). I've got friends and contacts on there, but I don't really interact with anyone through that site all that much.
I have been considering getting a MySpace account, but not for the social networking aspect - there are some bands I like on there, and that way I could find out what/when/where stuff happens. It's not a priority right now, though.
The rest, I'm simply not interested in, I'm afraid. I don't see the point in finding ways to waste more time online than I currently do. And I have other ways of keeping in touch with my friends.
BTW I'm going to add you on Flickr now. :P