Feminist philosophers of science have been prominent amongst social epistemologists who draw attention to communal aspects of knowing. As part of this work, I focus on the need to examine the relations between scientific communities and lay communities, particularly marginalized communities, for understanding the epistemic merit of scientific practices. I draw on Naomi Scheman's argument (2001) that science earns epistemic merit by rationally grounding trust across social locations. Following this view, more turns out to be relevant to epistemic assessment than (...) simply following the standards of "normal science". On such an account, philosophers of science need to attend to the relations between scientific communities and various lay communities, especially marginalized communities, to understand how scientific practices can rationally ground trust and thus earn their status as "good ways of knowing". Trust turns out to involve a wide set of expectations on behalf of lay communities. In this paper I focus on expectations of knowledge sharing, using examples of "knowledge-sharing whistleblowers" to illustrate how failures in knowledge sharing with lay communities can erode epistemic trust in scientific communities, particularly in the case of marginalized communities. (shrink)