I've had a circular barbell in my left nipple for years. If you want them and think they'd look nice on you, get them. Just the idea really squicks me out. Tori Black videos. There is a chance that you may be forced to lift your t-shirt and show them to the agent in a public space, but that's not the big deal for most men that it would be for many women. I once dated a guy with nipple piercings.
No, but I suspect they're a pretty small minority.
For me it depends on the physique of the guy and his general demeanour. Ears are pretty sensitive, and considering the dangly types of earrings that so many people wear, I can't imagine nipple-piercings being prone to snag more often. Also, I shudder at the thought that someone might accidentally take a grab at you and rip one off.