Hmmm if OpenLedger is decentralized - and has USD pairs that the site claims are backed 1 - 1 with real dollars, who is holding the cash?
Also, fiat w/d and deposits are currently disabled, so how are they trading in them? Are they Tethers and not dollars?
Those are bitUSD/bitEUR/bitCNY/bitBTC/bitGOLD/..., they are called Smart Coin in bitshares terminology. The collateral is decentralized. Every Bitshares user can lock some BTS as collateral to issue smart coins. No central point of failure.
More info here: https://bitshares.org/technology/price-stable-cryptocurrencies/
Currently Fiat deposit is closed, but you can deposit many other tokens, they will be guaranteed by openledger (so centralized). Then you can sell it for a smart coin to avoid the risk of default of openledger. You will then be able to go out through another gateway (rudex, cryptobridge, ...)