Has anyone considered that the Christmas Day bomber and the Times Square bomber DELIBERTLY “failed” in their attempts? Both have succeeded in their main purpose - fear.
Perhaps a successful bombing would trigger a massive military response that they do not want. A “failed” bomb attack instills fear and is just as successful as a real detonation, without the unintended consequences.
Judging by the state of “homeland defense”, the war against the Mohammedans is almost over - and America has lost. Consider this - radical Mohammedan “schools” operate freely; anti-American groups (like CAIR) openly advocate fot the violent overthrow of the government; public facilities have been modified to accomodate Mohammedan prayer; and finally, it is NINE YEARS since the World Trade Center was destroyed. There is STILL a giant hole in the ground to remind us.
“Without the unintended consequences?” Which means with the intended consequences, right? More fear is generated by a deadly explosion than by a failed attempt.