Trust is an important problem in agent-mediated electronic commerce. Many definitions of trust have been provided in the literature and almost as many models for trust management have been described. However, much of the literature deals with empirical evaluation rather than formal analysis. This talk will describe several problems in trust management, and describe a formal, game theoretic trust model formulation for which analytical results have been obtained. Within this framework, several prominent trust models are compared and shown to be exploitable as formulated. Finally, the Adaptive Exploitation Resistant (AER) model is described that has improved properties of resistance for specific classes of model attack.