but I'm quite certain the vast majority of these teenagers/twenty-somethings getting a zillion piercing are SO going to regret it later
Actually that's one of the good things about piercings, is that they are removable. I've removed several piercings that I later decided I didn't want. Yes, it left a scar, but the scars are so tiny that they are hardly noticeable. It's just two little dots where the peircing was.