Any decentralized system which is not purely trustless will be inferior than centralized trust systems. The reason of bitcoin's success is not only that it is decentralized, but also it is trustless. All these efforts like Bitsquare.io or OpenBazaar has failed to be purely trustless and relying on an arbitrator. IMHO, as soon as you bring in human interference you are no more trustless and just a flavor of centralized trusted systems.
But the arbitrator is decentralized. Anyone can become an arbitrator, all they are doing is confirming a transaction just like a mining computer would confirm a transaction.
Not sure about OpenBazaar, but arbitrators maintain a hierarchical structure in Bitsquare.io (ref:
https://bitsquare.io/arbitration_system.pdf), which is very much like BitcoinTalk's Trust system. They have a supreme court type of thing, which can be compared with our DefaultTrust. Now, imagine some CanaryInTheMine will be sitting in that supreme court. How will he try to f**k around the arbitration system for his own profit ? This is impossible in bitcoin network, because there is no human judgement. Same is impossible in decentralized exchange/marketplace because FIAT transfer is always requiring manual approval (unless we can have a fixed value ALt).
I only read the OpenBazaar paper on it. It looked quite decentralized. I need to read more on the BitSquare setup.