  Many markets rely on traders truthfully communicating who has cheated in the
past and ostracizing those traders from future trade. This paper investigates
when truthful communication is incentive compatible. We find that if each side
has a myopic incentive to deviate, then communication incentives are satisfied
only when the volume of trade is low. By contrast, if only one side has a
myopic incentive to deviate, then communication incentives do not constrain the
volume of supportable trade. Accordingly, there are strong gains from
structuring trade so that one side either moves first or has its cooperation
guaranteed by external enforcement.
