This article looks particularly relevant for Bitcoin:
Reputation Systems for Anonymous Networks
Elli Androulaki, Seung Geol Choi, Steven M. Bellovin, and Tal Malkin Department of Computer Science, Columbia University
{elli,sgchoi,smb,tal}@cs.columbia.edu
Quote
Abstract. We present a reputation scheme for a pseudonymous peer-to-peer (P2P) system in an anonymous network. Misbehavior is one of the biggest problems in pseudonymous P2P systems, where there is little incentive for proper behavior. In our scheme, using ecash for reputation points, the reputation of each user is closely related to his real identity rather than to his current pseudonym. Thus, our scheme allows an honest user to switch to a new pseudonym keeping his good reputation, while hindering a malicious user from erasing his trail of evil deeds with a new pseudonym.