I don't post here much at all these days, but this topic took my attention. I won't try to argue my point with long wordy scientific reasonings or bore you with my detailed stories of my accidents, but.....From personal experience from my worst accident, (hit by a car doing 50mph from behind, fract vert, leg and head injuries), my helmet did two things:-

1: If you can imagine me being flung through the air after impact and landing on my head, the helmet saved my skull from cracking like an egg shell, it did the job it was made to do, even though it was shattered into 5 pieces and blood soaked. It didn't protect part of my left ear which was gouged away, plastic surgery is a marvel isn't it?

2: The straps of the helmet sliced part of my scalp to ribbons, right to the bone. I now have some nice scars...if you want some pics......

All in all, I wear a helmet to obey the law here in Oz and to protect my noggin....simple.