The problems is 3rd party trust.
A decentralized exchange in the style that Bitshares is planning will solve this.
No more Gox. No more need to trust anyone.
There will still be the need for conversion from fiat to cryptocurrency and vice versa, unless BTC or another cryptocurrency becomes very widely used and people get paid in it. A lot of people kept their BTC in their own secure wallets but when they transferred it to mtgox to sell for fiat and withdraw, their withdrawal wasn`t processed.