I'm cool with piercings on teens of either gender. I don't like pierced ears on younger boys, but I honestly hate pierced ears on little girls too.
When kids are old enough to actually own their fashion choices, I'm pretty much an "anything goes" kind of person as long as those choices aren't sexually provocative or inappropriate for a specific setting. My SD is 14 and has double piercings and has dyed red streaks in the underside of her blond hair for a couple of years. I think the look is a bit cheap and trashy, but she likes it and cleans up nicely for holidays and family functions so...whatever. If my 14 year old son wanted his ear(s) pierced I would have no problem with.