In my opinion, the hand waving happens when people associate the "flash crash" with HFT in particular. Algorithms may have behaved as designed, but a lot of hu

In my opinion, the hand waving happens when people associate the "flash crash" with HFT in particular. Algorithms may have behaved as designed, but a lot of humans panicked. Yes, this panic led to some people losing money, so obviously any smart algorithm designer would build in some common sense controls. There is no reason to believe that it was only HFT algorithms that dealt poorly with the panic scenario.