Mtgox cannot print money. I think you've got them mixed up with the federal reserve.
MtGox most definately CAN print money. The number they show you as your balance at MtGox can be purely printed money which they cannot back up with anything.
*sigh*
You've still got them mixed up with the federal reserve. The fact that both of them are full of hot air does not make your point
Setting aside the fact that the federal reserve isn't an exchange and can't Fail to Deliver (since they never promise delivery of anything in the first place!) for a moment: this isn't just supply+demand. If a bitcoin exchange announced that a ton of BTC had been stolen from it you'd see the same effect -- the BTC price at the exchange would go
up as people rush for the exits via the quickest escape route (BTC). But
if the exchange had half their USD bank account balances seized and froze half their customers' USD balances the effect would be the same -- freaked-out people would still rush for the exits by buying BTC,
even though tradeable USD on the exchange had suddenly become scarce.
This isn't about supply and demand, it's about final delivery mechanisms during times of crisis. Bitcoin is more final than the fiat currencies used during the last 50 years and quicker to move than the precious metals used during the previous 5,000-odd years.