Do you think a person who have such economic power wouldn't use that to manipulate the market for years?? think again...
if they've got that many coins why manipulate the market and risk decreasing their value? The only gameplan worth playing is the one where you just withdraw bitcoins. Anything else is just totally illogical. With 750k coins there is no point in trying to play games with the market and manipulate it. Sure you can cause some flash crashes but then what? That just creates more instability and you've not gained anything.
Anything else is just pure fantasy.
Nope.
If I had stolen 750K in Bitcoins, at was primarily interested in cash, I would of course have a pressing urge to enjoy the immediate benefits of cash richness, but unless I was stupid, I wouldn't dump so much that I destroyed the market which is to be my cash cow for the next 20 years or whatever. Nope. I would definitely let it grow before cashing in my next pay cheque.
If exchanges didnt require verification and you could just be anonymous, full on dumping would be the best choice. But since it isnt, then yes.. small dumps that suppress the market eternally are better.