Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

May 6, 2010 stock market decline/plunge: Why did it drop 9% in a few minutes?
Part of it was an Oops, but not all of it. There were reports that the sudden   drop was caused by a trader who   mistyped an order to sell a large   block of stock. The drop in that   stock's price was enough to trigger   "sell" orders across the market. Source: http://www.msnbc.msn.com/id/36983596/ns/business-stocks_and_economy/