There was some art house flick that played near me recently that was NC-17. And this is in a town where the title of "Kick Ass" was censored on the marquee!
First time I've noticed a NC-17 movie around here since the 90's. The local paper back then wouldn't even carry a listing for one. I'd like to think people have mellowed out over the rating, but you never know.
Having a adult guardian accompany a minor get the theater owner off the hook if the minor has nightmares for weeks afterward. Most chains check ages now, so kids sneaking into a R rated film is practically a lost art. Fangoria magazine once suggested kids pay for their ticket with a large bill, and ask about the snack bar.
There are so many movies with homoerotic elements that fly under the radar of the MPAA, I couldn't even begin to list them all. ;)