Motivated by the prevalence of online trade among strangers through consumer-toconsumer
transactions, we examine by random matching the theoretical possibility of a
social norm of trust and reciprocity emerging among strangers in the infinitely repeated
buyer-sender game. Players are completely anonymous and interact only at randomly
determined times. Based on the study by Kandori (1992), we show that the social norm of
trust and the reciprocation of trust can be sustained in a population of self-interested,
anonymous strangers when trust and reciprocity are attached to the community as a whole.
Sufficient conditions that support trust and reciprocity as a sequential equilibrium are
provided.