How Many Markets are Two-Sided?

There is a lot of talk nowadays, among competition policy practitioners, about two-sided markets and two-sided platforms. It is indeed one of the hot topics. Part of the interest arises from it being a relatively new concept and part is due to the claim from many economists that competition policy for two-sided markets should be different than for traditional one-sided markets.

For instance, a price below marginal cost should not be perceived as a sign of a preda