No, but I don't really understand not wearing a helmet.
Our sales pitch at work is, "I don't where one because I'm worried about my skiing, I'm worried about yours."
Seems to be pretty effective.
It's true that at a high speed fall, the helmet really won't do anything, but hit your head on a box or rail, slam it into a tree, have a loose snowboard slam into it; you will be thrilled that you had one on.
As far as mountains requiring, here all kids are required to wear a helmet in youth lessons. I think I've also hear the same about other resorts. I think this is fair. At Mt. High, all instructors and park staff were required to wear a helmet, at Mammoth, it's optional for instructors. I like the rule of all on hill employees wearing a helmet, sets a good example.