maximillianos - 4:26 pm on Dec 5, 2008 (gmt 0)

Not a bad idea, although you could probably guess based on demographics. If you deal with a sub-30 population, I'd predict high penetration. Particularly high if college grads, students, or college-bound.

I myself recently jumped on the Facebook bandwagon and I was very surprised to see most of my friends and colleagues already members (30's - 40's age group).

My guess... it is starting to catch on to the middle of the road generation as well...