Thomas L. Friedman asks: “With all these reports about the bungling of U.S. intelligence, and the C.I.A.’s relying on bogus informants with names like ‘Curveball’ or ‘Knucklehead’ or whatever, why have there been no terrorist attacks in the U.S. since 9/11? I’ve got my own pet theory about what’s produced this period of calm – and, more important, why it may be coming to an end.” (New York Times op-ed)