We present a trust-based mechanism for the acquisition of information from possibly unreliable sources. Our mechanism addresses the case where the acquired information cannot be verified. The idea is to intersperse questions (“challenges”) for which the correct answers are known. By evaluating the answers to these challenges, probabilistic conclusions about the correctness of the unverifiable information can be drawn. Less challenges need to be used if an information provider has shown to be trustworthy. This work focuses on three major issues of such a mechanism. First, how to estimate the correctness of the unverifiable information. Second, how to determine an optimal number of challenges. And finally, how to establish trust and use it to reduce the number of challenges. Our approach can resist collusion and shows great promise for various application areas such as distributed computing or peer-to-peer networks.