There is a little known gem of modern microeconomics called the Myerson–Satterthwaite theorem. It states that under certain assumptions (Bob knows what an item he owns is worth to him, Alice knows what it is worth to her, both values are drawn from some commonly known random distribution) there is no mechanism that will guarantee that trade takes place exactly when it "should" (when the item is worth more to Alice than to Bob) and that relies on truthful revelation by both parties.

That is, even when there is room for profitable trade, negotiations may break down because the only way to ensure the perfect outcome is for each agent to truthfully reveal what the object is worth to them, and there is no way to give people an incentive to do this in all cases.