The court erred by: (1) assuming that that the characterization of the Amex service as a two-sided platform should fundamentally change the antitrust principles that govern the Amex restraints, (2) misunderstanding the nature of competition in two-sided markets, (3) placing the burden on plaintiffs to disprove that the harm from supracompetitive merchant fees are not outweighed by benefits to third parties (cardholders in this case), and most importantly (4) disregarding the critical antitrust issue – the impacts of the Amex merchant anti-steering and pricing restraints on competition among credit card platforms.