The past few years have witnessed the multiplication of seminars, conferences and training sessions devoted to "research data" as well as the development of new infrastructures and the allocation of new financial means to manage them. In line with new policies geared towards "open science" and the “replicability” of research, the current movement for open data enjoins researchers to archive the data they produce and make them available to the public. At the same time, new regulations have emerged regarding the protection of personal data, which reinforce the administrative and bureaucratic constraints that weight upon field research, especially for those working on so-called “sensitive” topics. Finally, the rise of digital surveillance poses unprecedented ethical and technical challenges to researchers willing to secure their data and protect the anonymity of their interviewees. These recent developments place research data at the heart of major political and scientific issues. Faced with a number of contradictory injunctions (protecting data, making them available), researchers have engaged in controversies and debates. Given the many questions and concerns that the current “data moment” provokes, this special issue proposes to take a step back and reflect on our trade and practices: what are data really? What is their role in the work of human and social sciences? What are we (researchers and research personnel) meant to do with such data? And what does the current “data moment” tell us about the changing economics of science? The articles of this special issue make a first contribution to a reflection that must primarily be collective.