I've thought the same thing OldSchool...it's like they just knew exactly where I was even when I'm in my stealth loadout. Then, I started thinking like Manic stated - if I tended to hide in certain spots, I'm sure others do to. So, now if I stop for a few seconds, I try to avoid those "common" areas and look for the less likely places.
Now I do get tired of hitting people in the head a few times and then they turn and knife me. pfft