MtGox likely has more than 2 million. (most of that might be reserve, though).

Most of it is not owned by them at all. Being an exchange they keep large amounts of all involved currencies for the customers Wink

If they decided to sell it all, few people would even bother to withdraw

.

You would need someone to actually buy this many, you can't just dump 7 million coins at once, the market isn't that deep.

Dump 10000 coins a day, in half a year they'd have completed the dumping and the price would have crashed.