How Powerful is the Iranian "Oil Weapon"?

On March 27, 2007, a rumor that an American warship had been hit by an Iranian-launched missile spread through stock exchanges around the world. Before the details of the “attack” were clarified, the price of oil jumped more than five dollars a barrel, an increase of over 8 percent in just a few minutes. A few hours later, American authorities denied the report, and the price of oil returned to its previous level.