The platform cooperativism movement, which brings about the best societal effects of the so called ‘sharing economy’, is on the rise. Nonetheless, it is far from being popular and nothing indicates that it will. In this paper we investigate the economic mechanisms through which dominant platforms remain dominant and hinder the development of alternative platform cooperatives. We conclude that a crucial factor is the fact that the property over the data created in sharing economy platforms is private and exclusive. We then propose a policy that has three goals: curtailing dominant platforms’ dominance, fostering platform cooperativism and maximizing the beneficial societal effects that can be derived from exploiting the data generated in platforms. The policy is based on making the data generated in sharing economy platforms a common to which reciprocity licenses would apply.