The issue is that bin Laden and his supporters BELIEVE themselves to be at war with the entire civilized world. Given that, any atrocity they can manage can be justified by them.

Granted, they can't carpet bomb the entire East Coast with fleets of airplanes, but a dirty nuke in downtown Manhattan is nothing to sneeze at either.

Personally, I think bin Laden has been largely neutralized. If he is dead, his followers will continue to recycle old tape to make it look like he's alive, but that's only going to work for so long. If he is alive, he can't effectively command his people in real time without risking showing his head and getting it shot off. Even a cell call could be fatal. Bin Laden dead, or bin Laden hiding in a hut somewhere, afraid to poke his head out, is pretty much the same thing.