The drop in oil prices has been stunning, with both US and international crude pushing a 40% decline since June. Attention so far has been on supply and demand getting out of whack: The world has more oil than it actually needs, with various estimates of the surplus falling anywhere from 700,000 to more than one million barrels of daily production. The US is mostly to blame. The shale boom has poured an extra four million barrels of oil into the world since 2008. That helped the market weather chaos elsewhere, keeping oil prices remarkably flat. Oil speculators hold a special place in the minds of a lot of people, who see them as somewhere between the devil and heartless capitalists manipulating the world's most important market.