This paper contributes to the analysis of mergers in two-sided markets, in which a platform provides its service for free on one side but obtains all its revenues from the other. A structural model allowing for multi-homing of advertisers is developed to assess a decision of the French competition authority, which approves the merger of the broadcasting services of TV channels but prohibits the merger of their advertising sales services through a behavioral remedy. We show that ignoring the interaction between the two sides of platforms in designing competition or regulatory policy can result in unexpected outcomes.