The liberating promise of big data and social media for creating more responsive democracies and workplaces is overshadowed by a nightmare of election meddling, privacy invasion, "fake news" and an exploitive gig economy. Yet, while regressive forces spread disinformation and hate, "guerilla democrats" continue to foster hope and connection through digital technologies. This book offers an in-depth analysis of platform-based radical movements, from the online coalitions of voters and activists to the "Deliveroo" and "Uber" strikes. Combining cutting edge theories with empirical research, it makes an invaluable contribution to the emerging literature on the relation of technology and society.