Strategic Manipulation of Internet Opinion Forums: Implications for Consumers and Firms Model Extensions

This appendix analyzes an example duopoly setting, which is a direct counterpart of the monopoly setting analyzed in Section 2 of the paper. The analysis shows that the results of the paper are robust with respect to several extension of my basic model. Specifically: • Appendix A.2 studies a setting where, in addition to praising themselves, firms can bad-mouth their competitors. • Appendix A.3 studies a setting where there are multiple forums and each consumer only visits a subset of them. • Appendix A.4 studies a setting where firms can also imperfectly signal their quality through prices. Consider a setting where two competing firms, A and B, simultaneously introduce imperfect substitute products in a new market. Just as in the monopoly case analyzed in Section 2 of the paper, we assume that the appeal of each product to consumers is the sum of two independent components: a horizontal component (" location ") and a vertical component (" quality "). A product's location can 1