This US equity rally was driven by technically oriented buying from the Banks and the hedge funds. There was and still is a lack of legitimate institutional buying at these price levels. This was machine driven speculation enabled by the lack of reform in a system riddled with corruption, from the bottom to the top."
Translation: there's no real buyers in the market at the current price, so when panic came, there were no buys to prop up the free falling
link: http://jessescrossroadscafe.blogspot.com/2010/05/plunge-1000...