Money for nothing: Exploiting negative externalities
We show that existence of negative externalities among market participants competing for a scarce resource, a setting typical for electronic commerce and internet advertising, allows for emergence of the no-allocation equilibrium with positive revenues for the seller. A monopolist selling K indivisible items to a large number of unit-demand buyers who face negative externalities whenever their rivals get the items, can exploit these negative externalities. If the number of buyers is large enough, the no-allocation equilibrium emerges: no items get allocated, yet buyers still pay the seller to avoid a potential exposure to negative externalities. We provide conditions on the magnitude of externalities and on the level of buyer competition that yield optimality of the no-allocation equilibrium. In the context of internet advertising, the no-allocation equilibrium allows the monopolist seller of a limited number of ad slots to simultaneously (1) optimize revenues by collecting a small payment from each of the potential advertisers who are concerned with negative externality effects, and (2) ensure ad-free experience to its users. Therefore, our results describe settings in which ad-free user experience can be supported not just by charging users, but could be subsidized by potential advertisers whose ads will not be shown. © 2011 ACM.