if you see a girl with a belly button piercing, it is a pretty good indicator that she is willing to have her picture taken naked. and will have those photos posted to the internet.
don't believe me? goto GuessHerMuff (NSFW) and notice how many of the subjects have belly button piercings. i'd say 8 our of 10. if the first link doesn't work goto this one GuessHerMuff
nakid ladies - good.
metal belly buttons - bad, unless you want see her nakid. then you have to see the damn piercings.