My friend was riding her bike to work one day. She didn't want to mess up her hair [her own words], so she had her helmet on her pack, not her head. She didn't feel safe riding along the residential streets without her helmet on, so she rode on the sidewalk instead. A car backed out of a driveway and shhe hit it, and subsequently fell to the ground. She had an abrasion high on her forehead, in a spot that would have normally been protected by her helmet.

I gave her a lot of grief over this, including a finger-wag. I bet if she were back in Montreal, she would ride her velo sans helmet in the many bike lanes without ever thinking about it.