Social Networks rule the world

Ok it seems like everyone is part of a social network of some sort.  Is it changing the internet as we know it? You have myspace which basically started out as popular place for teens to chat and post information about themselves, now facebook has taken over as the most visited social network. Of course with the popularity if myspace and facebook you are going to have tons of followers trying to capitalize on the popularity of these networks. You have more targeted networks like active rain which is the top real estate community social network. Will these sites stand the test of time or are they just a stepping stone to something bigger and better?