Yesterday was Delete your Myspace account day. I don't use any of those social networking sites and therefore I deleted all of the sites that were left. I cancelled my Facebook account a few weeks after using it for a few weeks.
Social networking sites are flawed, but maybe someday we will find out a way to make this work, but it is not today.
If people want to communicate with each other they can use email, IRC, phone, IM or any other way. It's not needed to have another system for those things. Friendships are somethingthat can't be described in a simplistic database.
It is a lot more complex. Still the social websites have to try something, or they could stop of course.
Maybe the direction is wrong. They try to go from social network to being useful. Maybe they should try it the other way around: from being useful to social network.