[vidarh]

What protects against this is that if you put in a bunch of buy orders for BTC at high dollar amounts, a rash of people would rush to sell their BTC.

You might temporarily drive up the exchange price sharply, but at the cost of buy a ton of BTC at an inflated price.

[logicallee]

Of course, that's the cost. But how much do you have to spend in bitcoins to drive the price up that much?

e.g. buying $800K worth of bitcoin in 15 minutes, so that you can increase the price of BTC and then buy $5M worth of goods NewEgg - would $800K in fifteen minutes press newegg's btc-denominated price well below wholesale on those same electronic goods? (including to cover what you overpaid for the btc to execute your position.)