I was thinking this morning how when I crashed on my bike some time ago on a bike path, nobody bothered to stop. Nobody even asked me if I was ok, even though there were people riding past me in both directions (I had an audience when it happened).
I wasn't badly hurt, but I did have a bloody knee and thought I may have busted it. My bike was scratched up a bit, and my handlebar was twisted.
If you see someone who's crashed, would you not at the very least stop to inquire they're ok, rather than turning a blind eye and just going about your business?