High Frequency Trading machines are computer programs that can trade stocks at rates measured in fractions of a nano-second.
.GIF representation of HFT trading 2007 - 2012, created by Nanex (http://www.nanex.net/index.htm)
Nanex ~ The Rise of the HFT Machines
On May 6, 2010 - beginning at 14:42:46 and ending at 14:47:02 - the Dow Jones Industrial Average (DJIA) dropped approximately 600 points (5.7%), and then quickly recovered. The so called "Flash Crash" was traced back to high-frequency trading programs that over ran Exchange computer's ability to handle the volumes.
See Nanex's report on that incident here: http://www.nanex.net/20100506/FlashCrashAnalysis_CompleteText.html
Gif discovered via a Tweet (embed):
The rise of high-frequency trading, 2007–2012, in animated GIF format: nanex.net/aqck/2804.HTML
— Paul Ford (@ftrain) August 6, 2012
See also, Zero Hedge, 2012 Feb 06 | Presenting The "Rise Of The HFT Machine" - Visual Confirmation How SkyNet Broke The Stock Market On US Downgrade Day | http://www.zerohedge.com/news/presenting-rise-hft-machine-visual-confirmation-how-skynet-broke-stock-market-us-downgrade-day
.GIF hosted at http://www.nanex.net/aqck/2804.HTML