FT Alphaville has stopped staring at screens for just long enough to post the following:

That plunge in the chart above? That was the Dow going from -500 to -1000 in the space of seconds. We’re investigating.
At pixel time, the S&P 500 was trading off 4.2 per cent, and the Dow had come off its lows but was still down more than 400 points.
