First of all, we would like to thank Dominique Joye for his suggestions and helpful discussions throughout the writing. Our thanks also go to Michael Waidner of the IBM Security Research Group and Arnd Weber from the Special Interest Group for Multicurrency Electronic Wallets, who helped us to find social related information by sending us the CAFE report containing digital money related surveys conducted throughout Europe. Discussions with Uwe Wilhelm of the LSL at EPFL were also stimulating. Special thanks to Sonja Nießen for proof-reading the document.