It basically guesses that you are 30 plus or minus 5 years, so if you happen to be around 30 it's "eerily accurate."
29...I'm in my late 30's. No wonder I kick ass at Black Ops.
This test doesn't seem to be very accurate with trackball users. It guessed 47 for me, which is way offI use a trackball mouse, and it guessed I was 52. I know it's less efficient, but my carpal tunnel is totally gone now.
+5
I dunno, looking at the results here, it doesn't seem to be working that well...