What may have been thought to be workable in a vacant lot somewhere in Yemen was hardly a plan that was sophisticated or foolproof in the hands of a 'warrior' like Abdulmutallab. He had to get the device onto an aeroplane where it had to be yanked out of the trousers in the bathroom after being sat and sweat and farted upon for hours, then squirted with a syringe of acid, the syringe partly destroyed by the corrosive effect....
However, as the subsequent national stir made clear, it was still a success. The media became hysterical and the nation's political leadership overreacted, with the usual result. We got more vows of increased punishment to be meted out in the faraway place - Yemen - and were promised more technology and watch lists promised to keep the childlike populace safe.
link: Pants bombs vs America: The infernal conflict • The Register
...is, we will not succumb to siege mentality and by the way bend over, we want to X-ray your underpants.