Watching the US presidential debates (I've just completed the second), I notice Obama stating that the US needs to capture or kill Osama bin Laden ASAP.
While this would be a huge victory, I don't think that bin Laden is the be-all and end-all of Islamist terrorism.
Surely Islamism is an ideology, not a cult of personality. Wouldn't killing bin Laden just create another martyr or imprisoning him make the location of his captivity a terrorist target?
The nature of Al-Qaeda is a loose one and removing bin Laden would have little net impact on its overall capabilities.
This is not World War Two, where the suicide of Hitler led to the Nazi surrender eight days later. It's more like Soviet Communism, which was a system rather than a leader, not counting Stalin.