We argue that the traditional notion of trust as a relation among entities, while useful, becomes insu±cient in ephemeral ad hoc networks. In this paper, we address the challenge of extending the traditional notion of trust to data-centric trust, that is, trustworthiness attributed to node-reported data per se. We propose a framework for data- centric trust establishment: First, trust in each individual piece of data is computed; then multiple, related but possibly contradictory, data are combined; finally, their validity is inferred by a decision component based on the Dempster-Shafer Theory. We are especially interested in, yet not restricted to, ephemeral ad hoc networks, i.e., highly volatile systems with short-lived node encounters. We consider and evaluate an instantiation of our framework in vehicular networks as a case study. Our simulation results show that our scheme is highly resilient to attackers and converges fast to the correct decision.