I think huntersgirl was right about that not being a peeping tom. Rather, it is a bit of voyeurism, and I think you'll find it's real common with guys (and maybe gals, too). I know I'll look at a loose top or at the girl in a short skirt going up the stairs. I even like to "study" the form when the jeans are tight.

Don't know if girls do the same, but wouldn't surprise me if they check out a guys equipment or rear end. Ladies, is that true?