How about this: I wrote an article on having a kind of trust-less trading system. My goal was to make cross chain atomic swaps between Hive and bitcoin like chains but I couldn't work out how to do it. Hive doesn't have a scripting language at all. Because of this, I was unable to adapt Mike Hearn's cross chain atomic swaps into something that wouldn't ultimately leave one party trusting another at some point.
The escrow system of Hive is a second. People escrow send and the escrow agent can approve or return the money according to whether the other party sends the funds. The escrow agent is unable to just keep the money. But the agent could conspire with the holder of Hive to return the money even though the other transfer completed successfully. That's not good. If the agent is honest, there is no risk even if the traders are both dishonest or one is dishonest.
Even though Hive doesn't have scripts. It has multisignature. I could setup an account that requires signatures from your account, my account, and several other users' accounts. In this example, those users I listed could watch transactions on the other chains and approve escrow Hive transfers based on that. Except that all of these users would have to have programs watching so there would be enough signatures.
In this example, the single Hive user would have to conspire with several other users who would earn money from escrow transfers. A loss of real world reputation in Hive (not the rep score) would hurt them from earning Hive earnings and working as an escrow agent. It would seem really unlikely that three unrelated users would conspire in this way much less four or five.