Needless to say you always should wear a helmet when skiing, hardcore or not...
I've been also a hard core skier since I was a teenager (ie feel immortal and invincible !) and few years ago, skiing far off slopes, I personnaly help to rescue a russian guy whose life was clearly saved by his good quality helmet (almost exploded into pieces).
Without this proper equipment, even his mother wouldn't had recognized him...
Since that day I've always been wearing a helmet (that, BTW, I found to be surprisingly comfy)
Regarding Schumi, he's surely a very strong and healthy man, but I'm afraid brain damages are probably not the same thing as broken bones... Hope he will go through as good as possible, as quick as possible.