[anonymoushn]

Well, you can tell that they haven't bought all the orders that are under $600 because there are still orders on the book to sell for under $600. In particular, using only orders currently on the books of various exchanges, you could currently buy ~1600 MTGOX BTC at ~$300 and sell an equal number at ~$600. If you were Mt. Gox, would you take the free $480,000 or would you leave it?

Do I also have to be God to know that the sky is blue?

Edit: I suppose, based on your other reply, that you are contending that the orders on the books are already from Mt. Gox. I'm not sure why you would believe this, but let's pretend it is so for a moment. This leads back to the same conclusion: either Mt. Gox wants to sell BTC worth $600 at $300 and lose money, or they want to sell MTGOX BTC worth $0 at $300 and make money. Which do you suppose is likely to be the case?

[jellicle]

So, you made an assertion about what Mt. Gox is doing that is entirely unsupported by any knowledge on your part, I pointed out that you couldn't possibly know that, and your counter is that because Mt. Gox hasn't wiped out the entire order book in a particular direction, they must not be participating in the market at all.

Such brilliance.

[anonymoushn]

Sorry, there has been a misunderstanding. My first comment to which you replied could be rephrased as "There is a big arb opportunity which they are not exploiting, and it is interesting that they are not doing it." The continued existence of the arb opportunity is a public fact, which is why I was a bit baffled that it would be questioned. It was not clear to me at first that you believed I had claimed that Mt. Gox was not participating in the market at all.