This Article argues for reorienting many antitrust investigations-and more generally regulatory approaches-to focus on how control of personal data by corporations can entrench monopoly power in an economy shaped increasingly by the power of big data. What is largely missed in analyses defending Google from antitrust action is how Google\u27s ever expanding control of user personal data and its critical value to online advertisers creates an insurmountable barrier to entry for new competition. Moreover, Google did not just inherit that business advantage through its innovation in search engine technology. Rather, Google has aggressively expanded its control of user data both by moving into new product sectors to collect additional user da...