Quote from: bitboy999 on July 03, 2011, 10:18:55 PM

1. If I set up an offer e.g. "I'll buy 2BTC for at most $9/BTC", and at some point an offer appears: "sell 1BTC for $9/BTC", will my "buy" offer be executed partially or not at all? What if a "sell 1BTC for $8.9/BTC" comes in

I can only speak about Mt. Gox, but yes, you would buy 1BTC and have an open order 1BTC left.

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2. How does the exchange decide, which buy offer to match with a given sell offer? Is it oldest first? E.g. say there are 10 offer "buy for $9/BTC", and one sell offer comes in. Which of the buy offers will be fulfilled?

If you try to buy at $9/BTC then it would buy the cheapest orders first, and buy as many as possible until there were no more at $9/BTC or lower.

So if there was one person selling for $8/BTC for a single bitcoin, and another for $9/BTC for a single bitcoin, and you had an open order to buy 2 Bitcoins, you would buy the $8 and $9 dollar bitcoins, and you would have spent $17 (less than you were offering, which is good for you).

Just to add, I doubt you will be able to buy for $9/BTC ever again, but good luck.