The hardest hit I have ever taken to my head was on the plate ice when unloading chair 8 in vail. Someone caught my board withe their ski pole and it took my board out. It dazed me with my helmet. Without it, who knows. I had less dizziness when I got smacked with a 2x4 in a brawl once though.
I ride that chair 6-7 times a day about 5 days a week..... I always wear a helmet. I'd rather look stupid than be stupid. These days your in a major minority if your not wearing a helmet.