Donatella della Porta is Professor of Sociology in the Department of Political and Social Sciences at the European University Institute. She is the author of Corrupt Exchanges: Actors, Resources, and Mechanisms of Political Corruption (1999), and Transnational Protest and Global Activism (2004). Mario Diani is Professor of Sociology and Director of Graduate Studies at the University of Trento. He is the coeditor of Beyond Tocqueville: The Social Capital Debate in Comparative Perspective (with Bob Edwards and Michael Foley, 2001) and Social Movements and Networks (with Doug McAdam, 2003)