[Flame Of Liberty]

Are you guys sure it's just a couple of cents?

The disadvantage was that the "algos" had engaged in something other than what their claimed purpose is in the marketplace - that is, instead of providing liquidity, they intentionally probed the market with tiny orders that were immediately canceled in a scheme to gain an illegal view into the other side's willingness to pay.

Let me explain.

Let's say that there is a buyer willing to buy 100,000 shares of BRCM with a limit price of $26.40. That is, the buyer will accept any price up to $26.40.

But the market at this particular moment in time is at $26.10, or thirty cents lower.

So the computers, having detected via their "flash orders" (which ought to be illegal) that there is a desire for Broadcom shares, start to issue tiny (typically 100 share lots) "immediate or cancel" orders - IOCs - to sell at $26.20. If that order is "eaten" the computer then issues an order at $26.25, then $26.30, then $26.35, then $26.40. When it tries $26.45 it gets no bite and the order is immediately canceled.

Now the flush of supply comes at, big coincidence, $26.39, and the claim is made that the market has become "more efficient."

Nonsense; there was no "real seller" at any of these prices! This pattern of offering was intended to do one and only one thing - manipulate the market by discovering what is supposed to be a hidden piece of information - the other side's limit price!

edit added:

With normal order queues and flows the person with the limit order would see the offer at $26.20 and might drop his limit. But the computers are so fast that unless you own one of the same speed you have no chance to do this - your order is immediately "raped" at the full limit price! You got screwed, as the fill price is in fact 30 cents a share away from where the market actually is.

http://seekingalpha.com/article/1511...y-trading-scam