Saying it's decentralized is all well and good, but how exactly is that going to work? What is the technical mechanism that returns credits to the defrauded individual? What lines of software code actually implements it?
OK, sorry for the rambling, and I don't want to hijack the thread. Just imagine a centralized implementation of an insurance system then, since that's more straightforward. If I figure out a good mechanism for decentralization, I will post it separately.
I have spent some time and fleshed out my idea for a decentralized reputation system, and it incorporates your idea of using fidelity bonds and has some examples of network rules. Here: