The place of individuals and the control of their data have emerged as central issues in the European data protection regulation. The "empowerment" of the individual has notably resulted in the recognition of a new prerogative for the individual: the right to the portability of personal data. The corollary of this new right is the design and deployment of technical platforms, commonly known as Personal Cloud, Personal Server or PIMS, allowing the individual to consolidate all his or her data in a single system managed under his or her control. On the strength of these technical and legal innovations, several questions arise: what forms of empowerment are targeted in practice? What are the appropriate conditions to guarantee the objective pursued? At the crossroads of these questions, one dimension appears to be insufficiently exploited: that of "agentivity". This article transposes this notion from the social sciences to the management of personal data, and opens up a new reading of the empowerment measures of Big Data functionalities on personal data.