In a peer-to-peer system, large numbers of independent computers at the "edge" of the network (e.g., in user's homes and offices) share their resources (storage, computing, communication) to construct a powerful information or computing service. In this talk I will give an overview of some of the technical (and legal) challenges in managing data in such a system. To illustrate, I will use examples from some of our current research at Stanford. http://www-db.stanford.edu/peers