Trade logic: in the event that MtGox is kaput, this will go to zero; in the event that MtGox re-establishes operations, it will MtGoxBTC will move sharply towards parity with 'generic' BTC, which implies more than a doubling of this instrument.
Thus, if your subjective belief is that MtGox has a greater than 40% chance of surviving, this trade has a strongly positive expected value.
Finally: MtGox is scheduled to make a statement about their operations today (Tokyo time); there will be a rapid reaction to the *existence* of the statement before it's read - and that reaction will almost certainly be towards the upside. Last time that happened, is was good for a $100 move in this instrument in fifteen minutes.