i'm membersa lee you're watching "fast money" on cnbc much more right after this >>> welcome back to "fast money. it's been a wild week on wall street stocks getting slammed on monday for the worst christmas eve ever then yesterday the biggest point gain in history. and today a nine hundred point reversal the biggest comeback in a decade what's behind the swings in could it be the classic case of man versus machine check out the article from the "wall street journal" titled behind the market swoon, the herd like behavior of computerized trading pointing to the rise in electronic trading is this the driving force behind the huge point moves we'll bring in bob pisani for more on this we hear it all the time. >> i'm sorry, melissa, i know folks it looks scarey. the dow moves 800 points in an amp. how could it happen? there is a lot of players in the markets, folks one of the larger players are quaned funds but they have blends of stocks and bonds and commodities. all of then, all of them have levels at which they buy and sell assets. so for example, we saw clear signs in the last couple