The great interest in spatial data infrastructures (SDIs) has led to a wealth of SDI definitions in SDI debates. The article aims to contribute to both theory-oriented and practice-oriented SDI research by providing a critical re-examination of the SDI literature. Ashby's formal theory of regulation, which sees infrastructures as regulatory devices, is used to identify the strengths and weaknesses of several SDI definitions. This exercise shows how debates of the SDI objectives and the roles of users get caught in mantraps and also opens the door for a way out of this confusion by distinguishing between functional and adoption objectives. It also highlights the emphasis on technological components in the SDI definitions, which sidestep the importance of structural and human resource components in SDI.