I think it's when you pair the two fuck ups that you run into problems. I've just spent ten minutes defending the author to my only intelligent facebook friend so I won't go into detail, but his point that botnets could conceivably -- just through sheer reaction time -- do significant damage to the stock market shouldn't be ignored just because people also from time to time fuck everything up. I'm not sure where he's going with such grandiose language and his use of the word 'existential' was probably to his own detriment. EDIT: apropos of nothing, I've been meaning to ask you if you've read George Friedman' America's Secret War.So yeah - the algorithms fuck up. But humans fuck up worse, they fuck up consistently, and they often fuck up on purpose.