In our preliminary documentation on the matter, A pseudonymous trust system for a decentralized anonymous marketplace, we attempt to address some of these issues to preserve both anonymity and establish trust towards pseudonymous identities. Feedback is always welcome.
You ought to use a hybrid of WOT and a nash equilibrium strategy of mutually assured destruction through mutually risked funds. http://nashx.com/HowItWorks
The WOT give you protection from situations where there is a large discrepancy in the value applied to money its self by each party, and so the party that values the money less highly can extort the other party by legitimately threatening to destroy both parties risked funds. Its not a particularly threatening attack vector that would only work in very niche cases, but the addition of WOT would bring the likelihood of its occurrence down to almost zero.
The combination of these should be sufficient to create a very reliable totally distributed system of accountability even in within the framework of a totally anonymous system.