I am also annoyed by the helmet-on-the-handlebar phenomena. Haven't had a chance to say anything yet, but I'm more of an ironic kind: "Nice helmet," I'd say, pointing to the useless device.

What bothers me is people who wear their helmet (probably full of good intentions) while fully exposing their forehead. The helmet just covers the top/back of the head, like a kippa almost. Another useless device! (The helmet, not the kippa.) During my morning commute, I keep thinking about ways I could bring the topic up with fellow commuters, or fantasize about designing a set of post-it "tips for commuters" that I would leave on people's handlebars while parking my bike, which would include stuff like that.

*sigh*

I understand you, Mimi.