Through an update on its Facebook page Mt. Gox said that they are under heavy DDos attack and are working towards implementing a stronger solution that would defend the exchange against such attacks and an announcement will be made in this regards once it goes into effect.
Being the largest exchange Mt. Gox, based out of Tokyo, more or less governs the prices of Bitcoin. If the exchange is down or is unreachable prices of Bitcoin may not be updated as frequently and people would be trading on relatively old information. Because of unavailability of the exchange, there are times when traders start selling Bitcoin in bulk which causes panic and prices of Bitcoin start swinging to extremes.
The exchange has revealed that it is working on separating out the trading engine from the front end website that will not only better the working of the engine but make the engine less vulnerable to DDoS attacks.