[mrow84]

Somewhat farcically perpetuating the metaphor, is it not the case that Bill gets to know that Joe is interested in buying sheep once Joe has bought a few of them? And at that point Bill can outrun Joe and make money from his (very near) future purchases?

That was my reading of the article - it seems that either there is a flow of information from the trading events to the fast traders, or the scenario portrayed in the article was very unlikely (though I guess that couldn't be ruled out given how much trading there is). noonespecial's metaphor seems to apply, what have I misunderstood?

[twoodfin]

Somewhat farcically perpetuating the metaphor, is it not the case that Bill gets to know that Joe is interested in buying sheep once Joe has bought a few of them?

He doesn't know with certainty. He can guess that's what Joe is doing, but he could be wrong and be stuck with sheep that he can't sell for the price he intends to ask. Every second he owns sheep is a second he's taking a risk that they'll go down in price, not up.

[mrow84]

Yes, that makes sense. From what I understood of the article, and it really isn't my area so maybe I got something wrong, a buy order was not filled completely even though there were sell orders available to fill it. Doesn't that mean that people cancelled their orders whilst the buy was being filled, meaning that they must have been able to execute market actions out of order? That would put people who can act quickly at a big advantage on getting the price they wanted, because they can cancel and re-bid at a higher price. Sure it's a gamble, but it seems like one with little to lose.

I've probably misunderstood something, but it certainly seems to be an issue that gets people very exercised. I presume there must be some competitive advantage in being fast, otherwise people wouldn't do it, so surely the only real issue is whether or not the consequence of exercising that advantage is socially advantageous?