Quote from: Steve on July 31, 2011, 08:01:17 PM

Quote from: dsp on July 31, 2011, 07:24:25 PM

I don't think they can as the quote could be invalid as soon as you see it.

Example: Buy $100 worth of bitcoins at $13 ...if the trade fee is 1%, then the amount of bitcoins for the order would be $99/$13 or 7.6153 bitcoins (truncated to 4 decimal places). If the current low ask is $14, the then order is placed as "buy 7.6153 bitcoins @$13" ...if the current low ask is $12 and can cover my entire order, then it will execute a trade immediately, buying $100 worth of bitcoins (or $99/$12 = 8.2500 bitcoins).

This is by far the most common trade I do. I rarely sell bitcoins on the exchanges (instead, I like to spend or save them to spend later). And when I buy, it's usually for the entire amount that I have on deposit with the exchange (because I have no desire to keep a balance of anything (BTC or USD) in the exchanges).

When you buy AAPL from your broker they are actually giving you a quoted price. That is a price which is good for a certain amount of time and which they are guaranteeing themselves. They pay for this with a small fee (actually sometimes not so small).

Implementing this on a bitcoin exchange is both more difficult and more risky than the underlying exchange software, mostly because acting as a broker has significant legal implications where as exchanging currency for virtual goods does not.