With the way things are going at MtGox, I could see a large drop like that to occur. If they close down/stop trading I feel like the instability may cause a panic sell for a bit.
It'll bounce back quick though, so whatever.
If Mt. Gox did shut down, I personally don't think that would affect the price of BTC all too much. However, if a scandal will tons of collusion was discovered, I think that would be something that could drive prices down severely. I think horrible PR/public perception is a much stronger impetus than the shut down of a relatively archaic trading site.