Digital media and open educational resources (OER) are said to redraw the boundaries between learners and teachers, by weakening the centralization of expertise and the distribution of subject-matter authority. This paper presents the findings of an ethnographic study of how the use of OER mediates the relations between self-directed learners and facilitators in two online open courses offered at a non-formal educational organization. Findings highlight the different role played by OER in mediating the relations between learners and facilitators in the two courses. In one course, early-stage learners encountered difficulties in repurposing OER and needed help to move to a more advanced stage of conceptual understanding. In the other course, well-read participants used OER to develop an affinity space in which the facilitator was a fellow learner. The findings suggest that OER are better viewed as artifacts-in-interaction rather than resources to be delivered as they are to learners. Although facilitators at P2PU do not play the role of academic teachers, it is argued that the influence of OER on the facilitator role can have implications for that of the academic teachers as well.