Or similarly, an informal debt economy. If I give Bob a pair of boots, he'll be more obliged to give me one of his pigs when I tell him how nice and fat they lo

Or similarly, an informal debt economy. If I give Bob a pair of boots, he'll be more obliged to give me one of his pigs when I tell him how nice and fat they look a month later. Informal debt economies really only work within tribal communities where social pressure has more leverage, but it does solve the double coincidence of wants problem.