I'd have to say that about 40% of the Greenway cyclists that I see are helmetless. If that wasn't bad enough, nearly half of those want to remove one hand from the bars in order to be friendly and wave at me! For the love of Pete keep your hands on the bars! You're making me a nervous wreck!
I've seen too many experienced cyclists crash for no reason at all. So the "I ride within my ability" excuse doesn't cut it when you're riding on a hard surface with tons of unpredictable joggers, dog walkers, stroller pushers, fishermen, rollerbladers and other cyclists.
So if you're on the Greenway without a helmet and you wave to me I will ignore you. I want no parts of you cracking your noggin open.