I generally just dodge the lightless riders in the dark. Considering I can pick up an LED light for less than $4 that makes you nice and visible from the front, there's really no reason to be riding without a light.
I do generally slow down for someone having mechanical problems, and make sure they have what they need. I've stopped a few times to help other cyclists out.
I've also given away LED flashlights/bike lights on occassion to people that really seemed to need them at the time. (gave one away last night, in fact, to a lady who missed her bus and was going to walk home in the dark pushing a stroller.)
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"There is no greater wonder than the way the face and character of a woman fit so perfectly in a man's mind, and stay there, and he could never tell you why. It just seems it was the thing he most wanted." Robert Louis Stevenson
