and even considered normal unconscious behavior for males to do this. It's cited in the popular psychology book "Manwatching: A field guide to human behavior" (yes, I know what the title sounds like) by Desmond Morris (link:
http://www.amazon.com/gp/product/0810913100/sr=8-1/qid=1142977094/ref=pd_bbs_1/103-7068357-4869457?%5Fencoding=UTF8). It's more of a power play; men would prefer to feel they are in control rather than possibly be the subject of an unwanted advance. It might do a lot of men good to understand what it feels like. They'd be more sympathetic toward women in the military who undergo sometimes daily sexual harrassment.