About the gateways, if you’re dealing with a gateway you’re taking the same risk you would with a centralized exchange, however you could have a highly regulated trusted entity create something like CoinbaseBTC to be traded within Bitshares, while an actual bank could create Citicoin or CitiUSD to be traded, and within Bitshares you can trade real USD for real BTC in a decentralized manner.
So the decentralized exchange works, people are using it today, and it has never been hacked. So the benefit to the trader is you don’t have to ever again worry about the risk of holding your Bitcoins on an exchange where it can get hacked. And it’s very unlikely Coinbase or Citbank will be hacked but if they are they might be regulated and insured, and the hackers wouldn’t be able to do as much damage to you because you’d only be at risk when you withdraw into real USD or real BTC.
Example picture below of the gateway feature:
