Emerging networking technologies, such as community networks, mobility, ad hoc connectivity, mesh, ubiquitous computing, and other infrastructure-less networks, have an urgent need for a first-class set of features that address the problems of direct device-to-device introduction, authentication, and trust management. Traditional approaches have proven to be inadequate to address these needs, because these approaches rely on centralized or managed infrastructures, which are brittle or cannot scale. This article discusses the fundamental difficulties and system requirements for decentralized trust management. New technologies are proposed that enable the bootstrapping of trust, and, subsequently, the calculation of trust metrics that are better suited to these domains.