I have just one thing to add to this discussion....

Today I was on my mtb at the 4 way stop by my sons school. I take him to and from school via a cool dirt trail, so I was waiting for school to dismiss. I first watched as a woman on a cute little beach cruiser (orange and green, quite fetching- even had a basket on front) came to the 4 way stop. She was towing one of those covered kid trailers (burly type) with two little ones in the back. Not a helmet to be seen! And the kicker- there was traffic at in the intersection and she cruised right through without stopping!
I just remember thinking to myself "that woman should be brought up on child abuse charges!".
And then a few minutes later a father on a mtb came up with one of those tag along bike things that hooks to the back. He was there to pick up his daughter. Well he had a little guy on the tag along thing and again, no helmets to be seen. He stopped to say hello. I bit my tongue for a minute and then I said to the little guy "hey dude. Where is your helmet? Gotta protect that noggin there" in as nice a tone as I could muster. The father rolled his eyes at me. So I looked at him and said "yeah, you wouldn't roll your eyes if you saw the collection of smashed helmets that I have at home from seemingly minor falls. I'm doing a program at the school trying to get the kids to wear helmets up here. I have a lot of friends that are alive today because of their lid." He just smiled and said "uhh huh" and then took off. And as he was trying to mount the bike it kind of fell over and the kid toppled off. I said "my point exactly" and just smiled.
Holier than thou attitude I had?? Yeah maybe. Some people go around trying to convert people to their religion, I preach helmet use...