[thrownawayhft]

And under the regulation we might have been required to ask at minimum $120 for that stock when it was trading at $100. If the stock had a big day and rose to $200, Nasdaq would just raise our ask to $240, or whatever exact amount the regulation required. The only risk compared to the old way of doing things was that someone would hit the stock with a huge enough order to blow through all liquidity in one shot on the way up to our ask.