Although the economics of multisided platforms has developed important insights for antitrust policy, there are critical respects in which the body of academic knowledge falls short of providing useful advice to enforcement agencies and the courts. Indeed, there is a substantial risk that recent scholarship will be misapplied to the detriment of sound antitrust policy, as evidenced by the US Supreme Court’s recent decision in American Express. In this note, I identify several areas in which economics research could potentially make significant contributions to the practical antitrust treatment of platforms.