750k is not inconceivable. What is inconceivable is that a significant portion of those "coins" were highly liquid. I agree that if the numbers are that high, it is largely in part due to the use of Gox as a web wallet. The fact that Gox was an exchange is not evidence in and of itself that all coins held there were readily available on the market. Just take a look at the order books -- it puts things in perspective.