Current big data practices are largely guided by deliberations concerning their efficiency, and optimisation. Yet there is another perspective. This book highlights that the capacity for gathering, analysing, and utilising vast amounts of digital (user) data raise significant ethical issues. Annika Richterich provides a systematic contemporary overview of the field of critical data studies that reflects on – corporate, institutional, and governmental – practices of digital data collection and analysis. It assesses in detail one big data research area: biomedical studies, focused on epidemiological surveillance. Specific case studies explore how big data have been used in academic work. The Big Data Agenda concludes by asking if data ownership can be reclaimed by citizens from being simply an assertion of a conception of rights to (user) data that is defined by technological domination. She argues data literacy and discourse ethics may contain solutions as well as a critique.