I was listening to a recent episode of Marketing Over Coffee and they mentioned the results of a demographic study (Pathways to College Network is the reference, I think) of MySpace and Facebook. Here's what they said citing the study...
"MySpace tends to be more minority than caucasion, more female than male, and tends to be people from more lower income households. With Facebook the opposite is true. It's more caucasion than minority households, older, and wealthier."
Pretty interesting. I haven't heard either of the two social networks so distinctly segmented along these demographic lines. If this is true, it gives some perspective on which social network is more fitting for your next promotion depending on your target audience.