Mind you, if they lower tick sizes, that means a lot more order cancellations. A market-making algo is simply a control system, taking in a set of inputs and s

Mind you, if they lower tick sizes, that means a lot more order cancellations. A market-making algo is simply a control system, taking in a set of inputs and spitting out a fair price that it is willing buy/sell something for. The number spat out is a rational one, that is then rounded to the nearest discrete tick. Smaller ticks = more jumps in the discrete output price = more cancellations/modifications. Which is fine, except the anti-HFT brigade seem to think a trading system that cancels 10000 orders and trades 100 times is the devil. It's not, it's about as remarkable as any other control system. You may as well express outrage that the cruise control system in your car adjusts the throttle ten thousand times a second. The only downside is that the exchange needs to cope with that level of traffic.