There are multiple terrorist groups affliliated with AQ, and while they share some common beliefs they still have their individual interests (motivations) and capabilities. It is fruitless to attempt to explain why another attack has not succeeded since 9/11 against the homeland, since there are countless variables involved, but I agree with David's post that various groups have attempted attacks since 9/11 that have been have been successfully pre-empted. Unfortunately good news apparently isn't news. Furthermore, if I recall my recent history correctly the purpose of the 9/11 attack was to draw us into a conflict in Afghanistan where AQ thought they could teach us a lesson. Osama was reportedly quoted as stating that he was surprised at the extent of the U.S.'s response and when he thought he was going to get killed apologized to his men. Who knows, it was media reporting, so take it for what is worth, but if the purpose of 9/11 was to drag us into the Middle East and South Asia they suceeded, but I don't think it is turning out the way that they anticipated. Another major attack on the homeland would not only provoke a firmer reponse (regardless of who gets elected), but further alienate the moderate Muslim world, which they were attempting to mobilize to support their bankrupt radical cause. AQ and the other extremists are clearly losing, it will take time, there will be set backs, but it is impossible (in my opinion) for them to win. We have seen the radicals surface in the past and they always end up defeating themselves.