Osama Bin Laden is a tapeworm infesting the nether regions of the world.
UBL is alive because the reality of "time" was on his side in the short run (because of where he, Zawahiri, Omar, G.H and a few other HVTs have eked out their survivals...the Pak/Stan border regions)....
But the clock is turning in our favor now...and one of these days (or likely nights) we are going to put guns on his pathetic as$ (or a JDAM)....
We have guys risking all 24/7, deep in Indian country trying to make sure such a day happens.