Is it a vain obscurity? Perhaps an ideology? Could it be an accident, such as a smiley face on a nipple? I find it an odd experience. it is a very dominant and bold statement to "wear" tattoos, but the process is highly submissive. Stabbing ink into the flesh. Allowing and trusting a stranger (at first) to boldly take your skin. Quite a feat many people still frown upon. I was once asked because of my hand tattoo if I was jewish..... what?
Just pondering after peering at so many different peoples ink.