You think it works?  Which system do you have in mind?  Yesterday I have been pointed to
http://privwiki.dreamhosters.com/wiki/Distributed_Web_of_Trust_Proposal_2#Trust_Metric - the one of the topic of #bitcoin-wot.  I doubt it works. But, it seems, I do not yet understand some key issues of this proposal.

In particular I don't understand how one reaches the conclusion "The design is resistant to a number of possible attacks on the trust network, such as whitewashing and slander via bogus identities."

For example, a simple design for self-promotion:  I use 20 identities, 19 of them completely honest, communicating with others. They all value number 20 very high in all regards.  Number 20 seldom does anything, but it there is a large contract, it cheats.

For every cheating, the cheater receives negative rating from the cheated. But all the other 19 nodes can give similar negative ratings to the cheated guy.  So it is the cheated guy who looks like a cheater (by majority of the ratings) and his negative rating for the real cheater looks like empty slander by a cheater.

But, anyway, the successful cheater may be simply killed, and a new one created.

One may think that as a consequence of this, the propagation rating of the 19 guards will decrease.  No problem, one creates second order guards. They recommend only first order guards, who never cheat themself, and so their external propagation rating remains high. They give high propagation ratings to the first order guards. But nobody else has any actual connections with them, so there will be no other ratings to them.  And only they highly rate the real cheater. 

So I think the claim is not really justified, at least I would like to see some more justification.