You deal with it the same way you do in real life. You don't do business with them. If I only trust dollars I can stick to dollars. But if I trust Brooklyn Greenbacks or the BACE, then I can use them. Not sure how this is related to the protocol as any paper currency has this issue also.
But part of the beauty of the current financial system is that most of the time if I use a trusted intermediary, I can confidently engage in financial transactions without having to build up a trust history.
Again, not sure how this matters as it seems like you are going down a path that is unrelated to the actual protocol. There has been discussion of Ripple on the agile banking list and other payment systems that rely on intermediaries, and OpenTransact could be used in those systems, but the issue is not inherent in the protocol alone.
If you can't solve that problem, your economy is going to have more liquidity than real assets. It's a hard problem.
Much respect for Pelle. But this won't fly until that problem is solved.