Maybe someone running somekind of website where donations are accepted could run this experiment: Put on your sign-up/logout or download page a donate feature, and pictures of you next to your children/pets/dependent whatever, or a picture of your old car/tv and some text saying "I'm looking for money to replace this", etc.

I think physical proximity is a factor, but the emotions involved are more like "I can't screw the guy" and "I should help the guy" or "I should be a good person and do this", so if you can make these feelings emerge...