decentralized exchanges seem to be a complicated solution to simple problem. The market is already solving the problem. MTGOX had to occur before we'd see more robust, transparent, and accountable exchanges. The market builds on each failure, and is stronger with each iteration. The market is the decentralization of bitcoin exchanges.
But it's not just about transparency and accountability, although those things certainly help. It's also about legal recourse...knowing that exchanges can't just disappear and take all your coins without severe legal ramifications.