My understanding was that an issue with quotes lagging behind at the NYSE precipitated a kind of "order avalanche" where NYSE's quotes appeared to be better tha

My understanding was that an issue with quotes lagging behind at the NYSE precipitated a kind of "order avalanche" where NYSE's quotes appeared to be better than the rest of the market, thus inviting more order flow, thus pushing their delay even further back until the NBBO spread was big enough to kick a spaceship through. I'm not an expert but I do love studying all sorts of systems and this seems like an extremely plausible explanation. Pinning it on the HFT bogeyman, less so. http://www.theatlantic.com/science/archive/2010/08/nyse-tech-delays-contributed-to-the-may-6-flash-crash/61987/ http://www.theatlantic.com/science/archive/2010/08/nyse-tech...