This research paper explores the impact that the access to, and free usage of, stored (mainly public sector) data has on society, the economy and on good governance, together with the implications of this new paradigm for modern-day governments. Although a number of recent research studies attempt to identify the benefits and drawbacks of open data, or to demonstrate its role in governance processes, there exists to-date no systematic attempt to both rigorously survey current literature to enumerate the areas in which open data has had an impact and to discuss its potential as a significant tool for policymaking. To address this research gap, and to highlight its intrinsic value to different actors, we examine the current state-of-the-art on the impacts of open data research and practice through a systematic survey of extant scholarly and practitioner literature. The first part of our study will present a comprehensive overview of the societal, economic, and political impacts of open data. We will then evaluate the new possibilities afforded by open data to policymaking, and conclude with a discussion of its role in open governance.