I've been thinking a lot about 'trust' and 'reputation' recently. (I presented a paper at the Boston Computers, Freedom and Privacy conference earlier this month entitled OpenPrivacy - Enhancing the Internet with Reputations.)
Trust is key to any anonymous network, indeed to any society. Pseudonyms that over time prove to be trustworthy develop reputations that smooth the process of finding the people/entities that are most worth dealing with - within any given domain.
Trust is not generally transitive, as I may trust an auto mechanic with my car but perhaps not to invest my money. Ultimately, we find that trust develops through prior experience and knowledge, is spread by word-of-mouth, is dynamic, and non-monotonic.
There's precious little useful research in the computer science literature on trust and reputations, perhaps because there's a need to understand some background in the social sciences as to what it is and how it works. But I'm excited that more effort is going in this direction. Here's a short Bibliography that I have compiled. Suggestions are welcome!