> But aren't the ad prices derived by live auction? It's not as if Facebook is pricing above market equilibrium to extract monopoly rents. There is a peculiar

> But aren't the ad prices derived by live auction? It's not as if Facebook is pricing above market equilibrium to extract monopoly rents. There is a peculiar dynamic as the market centralizes toward fewer marketplaces (for example two-sided ones like AdWords) such that buyers have to go there to find sellers and vice-versa, that results in sellers getting stuck in a race to the bottom, while buyers are stuck in a race to the top. It's like the dark mirror of the network effect. The market maker gets to siphon off the growing gap as fees of various sorts. Voila, monopoly rents. FB isn't a two sided marketplace, but buyers are definitely stuck bidding against each other which causes the market equilibrium to rise. And even if you broaden the definition of the market fairly generously such that FB doesn't have a monopoly per-se, you've still got an oligopoly at best.