I just found an idea for Web -2.0. Or Web 3.0 (ooops, that’s already taken). Or whatever number you put on it.
Let’s reverse the “friend” relation. Let’s make all people friends by default, then allow them only to “unfriend”. This way your database doesn’t grow when people friend each other – you just keep the non-friendly ones.
Then you add extra thing: hate relation. Not that you’re not frined with somebody, you simply hate that guy.
Maybe you can even put a special christmas feature: I kill you.