For the perpetrators of 9/11, their biggest victory, far and away greater than they could've imagined, was the creation of the "post 9/11 world".
The most patriotic and best way to defeat them would've been to continue on with life as we know it. The massive overexpenditure on defense and homeland security and loss of one of the most American of concepts that most seperates us from the terrorists--civil liberties--that was brought on by the government's response to 9/11 is what has largely helped contribute to the mess we are in today.
Nym, with all due respect, it's very naive to think that a lot of what happened as a result was unnecessary. They weren't going to just give up because we carried on. I'm not saying that some of the results haven't encouraged them but barely responding in terms of security would have only led to more successful attacks.