If lawmakers cannot figure out the relevant market for Amazon, then regulators can easily misclassify or narrowly define the relevant market to deem it to be concentrated and, therefore, in need of a government remedy to fix a market failure. While changing antitrust laws would make it easier to punish Amazon or Facebook, it will also make it easier for the government to target any disfavored business. The collateral damage from lost competition will negatively impact consumer welfare.
