Recent scholarship re‐casts the value of data from financial to value in use, where value is a multi‐faceted, dynamic, emergent construct, co‐created by stakeholders. To date, the dynamics of the co‐creation of value from the use of personal data have been investigated from the starting point of use. However, personal data do not have inherent value, rather their value emerges during design against projected future use. We conducted a case study of the development of a personalized e‐book and captured the different perceptions of the value of personal data from firm, intermediary, and customer perspectives, namely means to an end, medium of exchange, and net benefit, respectively. The diversity of perspectives highlights ontological differences in the perception of what data are, which in turn creates epistemological tensions and different expectations of the characteristics of data embedded in value co‐creation. By detailing how the value of personal data is co‐created in practice, we argue that co‐creation during design creates conditions for sustainable data value necessary for the continuing operation of products and services based on personalization.