This is not very reassuring, nor would it want me to be comfortable trusting my hard-earned money at the marketplace.
If an arbitrator must be "voted in" by existing arbitrators then someone could potentially buy up a lot of arbitrator accounts to create additional arbitrator accounts which would further the attacker's ability to scam.
Seems pretty far stretched IMO. Keep in mind there will be a reputation system for arbitrator. Buying a lot of good reputation to make scams wouldn't last very long before any body figure it out and all reputations of these account will be affected. That would be a very costly and risky scam operation.
Someone could buy up a bunch of accounts with positive reputation and these accounts with positive reputation would vote their "scam" accounts to be an arbitrator. The accounts that are purchased would continue to act honestly, but the accounts that were "voted in" would not be honest
It would still require the scammer to highjack the whole voting pool. How many accounts would need a scammer to vote himself as arbitrator every single time? At what cost? It still seems far stretched to me. If the arbitrators that vote are chosen through a random process among the best reputations, that would make almost impossible such attacks.
Such an attack would cost nothing. All an attacker would have to do is buy up a lot of accounts with good/a lot of reputation, use the accounts with good reputation "honestly", vote in additional accounts that can work as escrow, scam with the newly voted-in accounts, then sell the existing "honest" accounts at the same price they were purchased for (or potentially for more as they would have theoretically gained additional reputation by continuing to act honestly).
This is a very similar vulnerability that PoS altcoins have
You still need to put a lot of money upfront taking the risk that you'll be able to sell all of them at the same rate.
Again. It is pretty far stretch to assume someone will buy enough account to be able to
the whole pool.