Acknowledgements The four debates collected in this volume were originally hosted by the EUDO Citizenship Observatory and its successor, the GLOBALCIT Observatory and then published as Robert Schuman Centre Working Papers. Each of the debates was co-edited by myself with the authors of the lead essays introducing them. The Forum ‘Citizenship for Sale’ was kicked off and co-edited by Ayelet Shachar, the Forum ‘The Return of Banishment: Do the New Denationalisation Policies Weaken Citizenship?’ by Audrey Macklin, the Forum ‘Bloodlines and Belonging: Time to Abandon Ius Sanguinis?’ by Costica Dumbrava, and the Forum ‘Cloud Communities: The Dawn of Global Citizenship’ by Liav Orgad. I am very grateful to them for agreeing to this book publication as well as to the altogether 45 authors in this book who engaged with the controversial questions we asked them to answer in a spirit of a respectful and frank debate. My most profound thanks go to Jelena Dzankic, Jean-Thomas Arrighi and Vesco Paskalev who were involved in these debates at different times as coordinators of the EUDO Citizenship project, as well as to Anna Kyriazi who has provided extremely competent and reliable assistance in editing this book. Rainer Bauböck v