I think that the anonymous surfers are less concerned with admin seeing their IP addresses than they are about the general membership. Wi_fighter is right that you can change your preferences to make you "invisible", but lots of times the anonymous surfers just haven't taken the time to register or log in. I have a couple of computers in my house and if I haven't closed the browser on a computer that I used to log in, it won't let me log in on another computer, so I'm anonymous sometimes, involuntarily.