Interesting.
This would certainly appear to be an offer at much better than market rates, since fair value looks to be more like 
Bitstamp-rate/Gox-rate ~ 660 / 280 = 2.35 to 1

Of course, that assumes that the transactions taking place on the MtGox exchange are all legitimate. 
How exactly would we conduct this transaction?  Didn't Gox suspend internal transfers?

There might be another way for you to make the same bet (that Gox is headed to 0), although the volume you're looking for could be a challenge.  Have you looked into options on the Gox price?