I can attest that a helmet won't do you much good if you do a face plant into the pavement at 20+ mph. That said, in the accident where that happened I must have bounced and hit the back of my head - there was a big indentation in the rear of the helmet, I don't remember anything after the front wheel went sideways on me. I woke up with EMTs hovering over me asking how many fingers they were waving in front of my face - being what I am even in that situation I was tempted to ask "Fingers or tentacles?" Instead I answered correctly and asked what we all do - "Is the bike okay?" Not a scratch on it of course - whereas I looked like Darth Vader sans helmet. I'll never ride without a helmet.