Many commentators have said that the reason for the 'flash crash' in oil prices is due to Osama Bin Laden's death.
"The killing of Osama Bin Laden may have been the catalyst for this week's rout in oil prices that's deflating commodity prices around the world," an article on Bloomberg read.
It seems unlikely that Osama's death had much to do with the slide in commodity prices. It is thought that "the death of bin Laden… changed the focus to the demand picture, which is worrisome".- Bloomberg
The real reason is suggest that the sudden drop in commodities is due to 1) concerns about the eurozone (Portugal, Greece and Republic of Ireland), 2) gains in the dollar and 3) rising US inventories of oil.