These would be NXT hubs running open source service modules. It wont be for everyone, but I would trust NXT hubs to work properly (after they have been tested) with minimal issues as compared to some places.
What if there is a glitch in the hub and the payment aren't received?
And if the node doesn't send the request to it's service module?
This isn't a trustless system.
No one should trust such a system.
"What good is complaining to bter?"
I can move to a different gateway if it's not good.
At worst you can stop using this setup if its not good, so I dont see how it is any worse.
In order to be reliable it would need to verify the external blockchain to make sure payment was made. proper error handling is certainly expected. Not impossible to do by any means. Source code review will allow people to verify the error cases that are handled or not handled. THIS is what provides a lot more trust than blindly relying on centralized exchange.
The code that the node is running is also open source. It would be tested and so the only way I can think of that the node doesnt send the request to the service is if the server crashes. Thats a good catch! So we clearly need to have a mechanism to make sure that important tasks are denoted as such and the NXT hub servers will need to verify that all services that were supposed to have been done were done exactly once. I think this is similiar to the double spend problem, tricky but not impossible.
Maybe Evil Bob will do horrible things? So yes we need super smart guys to make sure Evil Bob cant do really horrible things. I personally would trust that a peer reviewed open source solution that takes into account the Evil Bobs of the world will be more trustworthy that trusting some random employee at some random company. But, hey that's me. Maybe I am becoming a cryptoanarchist?
James