How does V4V work if not via the altruism of participants?

True, and I'm also curious whether it was self sustaining or whether it operated at a loss and was funded by the generosity of the owner.

At small scales, funding things like this out of your other income is feasible.  But try to do it at a large scale in an urban area and it's probably a lot harder to sustain.

SimpleStacker

To be generous, I think it's because they like people and sharing in the abstract so want an impersonal system vs someone helping themself to the food in their fridge.