Facebook=MySpace for adults ...who don't have any unusual hobbies.
IE None of us on this forum.
Basically...I have both. I use neither regularly. I use Myspace infrequently. I use Facebook NEVER. I have one so people can contact me if they want to, long lost friends and acquaintances, etc. But if someone tags me in a photo? I untag it. If someone associates me with anything, I try to undo it.
MySpace is based off nicknames. If I google my full name, my MySpace does not come up. Not so with Facebook. Potential employers now often make a habit of checking people out on Facebook. It's no good. I would turn off so many potential employers by my fashion and hobbies, just by my music choices. Some may say I'm selling out by hiding them...but I don't think so. I just keep work and play separate (except when I type on DGN at work... ).
A potential employer needs to know my skills and talents and how I would fit in their team. Not what kind of clothes I wear or what I do on Saturday nights. As long as I show up on time and not hungover on Monday morning, dressed appropriately for work, that's enough.
But as someone else said, the only thing I actually use is LiveJournal. Hell, I use Mixi more than Myspace.
Honestly, at the moment I'm probably far more searchable than I'd like to be, in a perfect world, even as it is. Facebook is like just asking to be searched.