He has never passed up a photo op in the past and has been noticeably absent since December..
The most recent videos of him could be easily engineered using rudimentary editing equipment.
He is worth more to the terrorists in "limbo status" because he is our "boogyman". We are spending our resources trying to prove he is dead rather than preventing more like him from living...
On the contrary, this is the best case scenario from the U.S. government's point of view. No one knows for sure that he is dead, so any "dead-man switch" plans that Al Qaeda might have developed remain in limbo. The lack of evidence allows the U.S. to continue to hunt for him, and in the process capture other Al Qaeda leaders, without the opponents of the War on Terrorism being able to claim that the war is over because we've already eliminated the ringleader. It also makes it more difficult for other individuals to openly claim the mantle of Al Qaeda leadership, since that would be an admission that he is dead. And meanwhile Bin Laden just slowly fades away from everyone's consciousness...