This prototype had a single arbiter per transaction, but there is no reason why you couldn't have N arbiters on each transaction, for as high an N as you want.

This prototype had a single arbiter per transaction, but there is no reason why you couldn't have N arbiters on each transaction, for as high an N as you want. Imagine having, say, three arbiters for each transaction, and two of the three have to side with one side in order for the money to be moved. This cuts down a lot on the potential problems, especially if the arbiters were kept anonymous from one another, thus preventing collusion and making sure that each investigation is independent from the others.