Selling 1,000,000 coins on MtGox right now would take the price down to $0.10, with an average price of $19.64, so you'd net $19 million.
Of course, what would really happen is that everyone would see it happening and cancel their bids before the wave reached them, so you'd likely not be able to actually sell them all at once.
Leaking them out a few thousand a day, though, would be completely possible. And if done correctly need not move the market at all.
I disagree that 1M coins could not be sold very quickly on MtGox. Yes, the price would go way down, but there are plenty of interested buyers who would be happy to "cash Satoshi out" to take some profits; he would certainly get serveral millions of dollars for his coins.
The bigger problem is that selling on MtGox requires identifying himself to create an account (not to mention the current $1,000 per day withdrawal limit for USD).
