One thing Osama bin Laden succeeded in teaching his Al Queda savages (before he went off he cavort with virgins in Paradise) is that America's chief vulnerability is economic, not military. Bin Laden, the son of one of the richest men in Saudia Arabia, was an astute businessman, and probably understood economics better than any other caveman terrorist in history. He knew the damage to America that would result from an attack on the WTC.

Now it appears that Al Queda has shed its prior reluctance to attack oil related targets (bin Laden considered oil as a symbol of Arab power) and recognizes the potential economic damage to America and Europe by threatening shipping lanes. If this happens again, it's a good bet that oil prices will rise.