Facebook or MySpace? How about other social networking sites?

I came across this question on Yahoo Answers. Really, I don't prefer one over the other, I just happened to have been on Facebook longer. I'm still getting used to the page format of MySpace. Read my earlier entries on these subjects. I'm now wondering who uses other social networking sites. If anyone uses other sites, how are these? Does it seem redundant being on more than one social networking site? One I've been curious about is Bebo-- anyone use that one? How about this--have you heard of that one? How about Xanga--anyone on that?