On Monday, suicidal truck bombers attacked three housing compounds in Riyadh, Saudi Arabia, killing at least 29 people, a mixed group of Saudis and foreigners. The tragedy, which U.S. Secretary of State Colin Powell says bears the "fingerprints" of al-Qaeda, marks a setback in the war against terrorism. But in the long term, it may actually hasten al-Qaeda's demise. For years, there has been no greater exporter, financier and ideological cheerleader of Islamist terrorism than the Desert Kingdom. By biting the hand that feeds them, the terrorists may have finally forced the Saudi royal family to abandon its subsidy of...