Digital Trust Networks

Overview
Digital trust networks are online systems designed to aid users in judging the characteristics, most notably trustworthiness, of other users. These systems vary widely in purpose and application. Early examples include the feedback mechanisms and reputation systems of online marketplace services such as eBay and Amazon Marketplace, whereby buyers and sellers can by judge each others' reliability viewing accounts of prior transactions left by other users. This method was later adopted by Hospitality Exchange networks such as Couchsurfing to help identify safe guests and hosts.

Resources
TrustLet - A wiki-based hub for research on trust networks