I'd wear a helmet for sure. Two days ago I was out skiing, now I know skiing isn't biking but something similar could've happened. Anyways, my skis got caught in some heavy snow and I ended up going down. I would've been ok but the skis popped up and I was sent flying, it ended with my head in a wooden post. The ski helmet is dented a bit and I was unable to move for a few seconds. Needless to say I was a little loopy too, today my neck and back are better but after the accident I couldn't read and my vision was really bad. I am convinced I could've been seriously disabled or even killed without a helmet, the helmet made the shock much wider I hit at the corner and would've split my head. Like I said, it wasn't biking, but I can see something similar happening. Please get a helmet!