Imagine of amazon quietly buys all the bitcoins from mt gox committee and then start accepting bitcoin as currency! If this possible? if yes, what flaws would it have?
[Edit : you are missing the FROM MTGOX part! I do not mean buy every existing coin in the world]
They don't necessarily need to buy bitcoin from MTGOX, but it would actually make a lot of sense for amazon to buy bitcoins and then announce that they would accept BTC as a payment method. I don't know if they could be accused of inside trading though, and that could be a problem for them.
They know they would affect the price of bitcoin, because if they announced they would accept BTC as a payment method, it's price would just skyrocket, and no one doubts that, so it would make perfect sense for them to be accused of inside trading, and face penalties.