The article is a bit suspicious. It talks about Thor, which timed orders to different exchanges so they'd arrive simultaneously. This is because a market maker

The article is a bit suspicious. It talks about Thor, which timed orders to different exchanges so they'd arrive simultaneously. This is because a market maker would notice a large order on one exchange, and raise his price. This is totally and utterly expected - why should a market maker take undue risk? Increase the latency - suppose a user submitted a large buy order to Exchange1, waited an hour, then sent it to Exchange2. Is it not reasonable that the price would go up? So why is it suddenly so controversial when it happens on shorter timeframes? Why should RBC be able to make big trades and not have to deal with price impact? Why should market makers be left holding the bag? Now whether or not HFT adds more value seems debatable. But it seems to be a fairly harmless result that naturally arises.