- He's under two thousand tons of collapsed granite. Kind of hard to get at. This actually answers most of the questions best, and barring new information, I see it as the most probable.

- A large number of the people around him, tribesmen in Afghanistan or Pakistan perhaps, either may not have heard about the reward, or have no idea how to go about claiming it even if they grassed on OBL.

- The tribesmen may have been convinced by OBL and others that the reward is just another evil American lie.

- Despite a reputation for being mercenary, the tribesmen may have certain things they can't be bought on as a matter of honor. Of course, if only one out of 500 men decides to blow the whistle, that's all it would take.

- The tribesmen are no dummies, and realize that showing up as an instant millionaire would paint one heck of a big target on your back. That target would still be there even if by some miracle you managed to get out of the country. And if you keep the money quietly in a bank and don't spend it, so no one knows, what's the point of having it? Some kind of Witness Protection program would have to be instituted along with the reward.