I used to be all anti-facebook for no reason really, I guess I just couldn't be bothered being on two of those kind of sites really (was primarily myspace).
Eventually I was dragged into creating a facebook and I find it to be more along my lines, myspace is too flowery/girly for me.. like, you don't need to customize your page or anything.
I only pop on to facebook/myspace to talk to people I don't see too much really, the whole put music on your page and customize the appearance thing doesn't really appeal to me.. my myspace looks just like every other myspace page haha, and I got a song on it, but I don't really get enveloped in that kinda thing.
More people I know for real use facebook, so I guess that's a major factor in me preferring facebook as well.
I don't use the internet to try hook up with chicks though, no need.