Let's say you're on a plane. That plane crashes and there are only a few survivals, in fact there are only two. You wake up after the other guy does, so he had enough time to collect and claim all the coconuts there were found in the island and he says he's willing to give you a set of coconuts, if you throat their ♥♥♥♥. Now, I'm asking you, would you consider that as a voluntary source of interchange?