With an increasing number of technologies supporting transactions over distance and replacing traditional forms of interaction, designing for trust has become a core concern for researchers in both HCI and CMC. While much research focuses on increasing trust in mediated interactions, this paper takes a systemic view to identify the factors that support trustworthy behavior. In a second step, we analyze how the presence of these factors can be signaled to allow the formation of well-placed trust. For our analysis we draw on relevant research from sociology, economics, and psychology, as well as empirical findings in HCI and CMC research. The key factors that warrant trust in another actor are contextual properties (temporal, social, and institutional embeddedness) and the trusted actor’s intrinsic properties (ability and motivation). In first interactions, trust is mainly warranted by contextual properties, as they provide external incentives and threat of punishment. As interactions are repeated over time and trust grows, intrinsic properties become more important. To increase the level of well-placed trust, researchers and designers need to identify signals for the presence of such trust-warranting properties that are reliable and easy to interpret. At the same time, they must be cheap to emit for actors whose actions are governed by them but costly to mimic for untrustworthy actors. Our analysis provides a frame of reference for the design of studies on trust in technology-mediated exchanges, as well as a guide for identifying trust requirements in design processes. We demonstrate application of the model in three scenarios: ecommerce, voice-enabled online gaming, and ambient technologies.