Lots of reasons not to do it. The main one being that it would create a shrine to the martyr.
On the other hand … and I can’t decide if my idea is laughable nonsense or if it’s a seriously good idea … if your objective is to look for terrorists, and you want to make it easier to find those terrorists, wouldn’t a bin Laden grave site be the ultimate “honey pot”? Anybody who would visit the location would instantly self-identify as an al-Qaeda supporter.
– uo
