Over the last two decades it has been argued that public relations contributes to hegemony by corporate organizations over stakeholder groups who have less power and resources. In its original formulation, the concept of hegemony had two defining features: firstly, it was conceived of as a society-wide, macroscopic formation and second as self-reinforcing i.e. self-replicating. This article argues that the rise of big-data in public relations is a hegemonic development that further re-enforces the current institutional logics and power in the three main spheres of society: corporate, governance and civic. Using the economic notion of externalities, the authors argue that loss of agency over personal data is the unpriced, unrecognized externality that drives the big-data market. This externality is dependent on those who are the losers of agency not having the requisite information, power or resources to negotiate alternatives that might re-dress the balance. As users and proponents of the use of big data, the public relations profession has a number of key questions to answer if it is not to re-inforce arguments that it is a hegemonizing force in organizations and society. Normal economic remedies to address externalities are not adequate to a case that is both ethical as well as economic in nature. The article therefore concludes with five arguments that the public relations profession should debate to provide leadership within organisations and society.