Quote from jimrockford:
I would say yes, to your first question. I believe that the recent spate of public reports, that IB failed to give price improvement in a situation where a competitor did give price improvement, probably was a direct result of IB not doing the particular type of hidden liquidity scan I just described. IB interacts with dark pools, but this is not sufficient to eliminate the need for the type of scanning I am proposing.
My belief, in response to your second question, is that IB does not get price improvement, withold it from the customer, and instead keep that price improvement for itself. I believe IB's assurances that its proprietary traders use the same SMART order routing algorithm made available to IB customers. I believe that IB is a basically honest company, that honesty is part of its business model, and that it acts in good faith with respect to order routing.
I would also say this. If IB does take the other side of a customer's buy (sell) trade, at the NBBO ask (bid) price, when in fact, the true hidden ask (bid) is a more advantageous price which would have been achieved by proper scanning for hidden liquidity, then IB does take a benefit for itself at the customer's expense, and I think this is a breach of the broker's duty to his customer. But I also believe that IB sincerely hasn't yet figured this out, and that IB is unaware it is doing this, and that there is no intentional wrongdoing, and that it is only a matter of time before IB does figure it out and make the necessary changes to SMART so that the situation will be corrected. I don't believe that any of IB's retail competitors are doing a better job of order routing than IB, even if there are some specific cases in which a particular competitor does better on a particular order.