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Many online businesses seek and provide attention. These online attention rivals provide products and features to obtain the attention of consumers and sell some of that attention, through other products and services, to merchants, developers, and others who value it. The multi-sided business of seeking and providing attention is fluid with rivalries crossing boundaries defined by the features of the products and services. It is also dynamic. Rivals introduce new products and services, some involving drastic and frequent innovation. Online attention rivals impose competitive constraints on one another. Product differentiation tempers the significance of these constraints in particular situations. But the relevant differentiation mainly involves aspects of the attention that is procured and sold rather than, necessarily, particular features of the products and services used for acquiring and delivering that attention. Antitrust analysis should consider these competitive constraints in evaluating market definition, market power, and the potential for anticompetitive effects. The existence of competition among attention rivals does not imply that antitrust should reduce the vigor with which it examines mergers and exclusionary practices among these platforms. It just needs to look for problems in the right places.
David S. Evans (Tue,) studied this question.