Mt.Gox, the largest Bitcoin exchange, is going to take measures to make the price of the virtual currency to better protect against manipulation. Thus, the trading engine will be better protected against ddos attacks. The last time there were repeated ddos attacks against Mt.Gox.
Another measure that Mt.Gox wants to take, is the setting of limits on the execution of small orders. The introduction of large numbers of small orders is used to other Bitcoin traders to give the impression that the price of Bitcoins drops. The api of Mt.Gox was used, but soon comes to an end: there may be a limited number of smaller orders in a certain period of time to be performed, depending on the Bitcoin market.
Mt.Gox is by far the largest Bitcoin exchange, where users of the virtual currency from the exchange. As a result, the exchange has a drawback, that the attention of malicious attackers. Not only are ddos-attacks; in 2011 it was the virtual exchange is still hacked.