This chapter argues that speed and reach are two key concepts of digital writing and rhetoric that span different media types and time periods but provide a critical explanatory frame from which to understand the power and the problems of digital rhetorics. It focuses on the relationship between ethos and trust in the rhetoric of digital writing in scientific and technical discourse. The chapter presents examples of scientific and technical discourse in digital settings, noting ways in which trust is established and maintained, often despite the lack of traditional peer review or expert input. For digital rhetoric and writing, medical discourse presents examples of both the potential and the problems with scientific information in digital settings. In rhetorical theory, trust can be viewed as connected to the appeal of ethos, which focuses on the character and credibility of the speaker and message.