The policies of opening research data are based on arguments of transparency, innovation and democratization of knowledge. This article aims to make their implications intelligible for communities working with ethnographic data, confronted with a transformation of the criteria for recognizing the credibility of the knowledge they produce. While researchers who practice ethnography are engaged in situated forms of sharing materials with peers, other disciplines and “source communities”, the strengthening of external control over the conditions under which this sharing takes place (...) destabilizes the economies of credibility that structure these practices. More than a reluctance to the process of openness, the withdrawal of ethnographers from the movement appears at the end of our analysis to be the result of both the existence of alternative ecologies of empirical materials and an ethic of the margins embedded in often implicit professional norms. (shrink)