Online feedback mechanisms harness the remarkable ability of the Web to not only disseminate, but also collect and aggregate information from large communities at low cost, to artificially construct large-scale word-of-mouth networks. Best known so far as a technology for building trust and fostering cooperation in online marketplaces, these mechanisms are poised to have a much wider impact on organizations. As discussed in the introduction, their popularity has potentially important implications for a wide range of management activities such as customer acquisition and retention, brand building, product development,and quality assurance. The study of such topics clearly falls within the domain of OR/MS