What's the deal with Osama???

Think Swamp Fox, Zorro , or Che Guevara.
Bin Laden is rapidly becoming myth. Sometimes that’s better than having a leader.

People unite when they are facing a common enemy or threat.  The mentality of this organization (and countless others) is that they are fighting the "Great Satan," or "the Infidel" ETC.   If bin Laden does die, the organization will believe he died fighting this "Great Satan" and they would have a new source of motivation.