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]
Why do they have to buy all of those Bitcoins from mtgox? and what is the point of buying huge amount of Bitcoin/cryptocurrency if they are earning a lot of money focusing with their business? Amazon doesn't need to do that, if they really planning to accept cryptocurrency soon, the only possible way that I think is they will partner with a payment processor since cryptocurrency price are not stable, for example amazon will accept Bitcoin, the third party payment processor will be the one to receive those Bitcoins then they will pay amazon in fiat currency or they will create and issue their own cryptocurrency.