A circuit breaker would do nothing for the exchange at this point. The way to solve this moving the trading engine to it is own server/program. It is right now connected to the front-end. Also the great thing about bitcoins is how open and free market it is, if bitcoin free falls to $0.01 it should be able. Just like it should be able to go to $1000, if the market dictates it.
When I read Nova's post I didn't think that he was suggesting that a circuit breaker would fix the exchange's problem, just like a real life circuit breaker doesn't fix the electrical fault in your house wiring when some dumbshit threw a toaster in the bathtub. It prevents the house from burning down.