 No matter how one conceptualises value practices, it is clear that their key role in data management and analysis prevents facile distinctions between values and “facts” (understood as propositional claims for which data provide evidential warrant). For example, consider a researcher who values both openness—and related practices of widespread data sharing—and scientific rigour—which requires a strict monitoring of the credibility and validity of conditions under which data are interpreted. The scale and manner of big data mobilisation and analysis create tensions between these two values. While the commitment to openness may prompt interest in data sharing, the commitment to rigour may hamper it, since once data are freely circulated online it becomes very difficult to retain control over how they are interpreted, by whom and with which knowledge, skills and tools. How a researcher responds to this conflict affects which data are made available for big data analysis, and under which conditions. Similarly, the extent to which diverse datasets may be triangulated and compared depends on the intellectual property regimes under which the data—and related analytic tools—have been produced. Privately owned data are often unavailable to publicly funded researchers; and many algorithms, cloud systems and computing facilities used in big data analytics are only accessible to those with enough resources to buy relevant access and training. Whatever claims result from big data analysis are, therefore, strongly dependent on social, financial and cultural constraints that condition the data pool and its analysis.