While Cryptkeeper's right, there are ways that the Taliban are capable of taking a pot shot at something and then rendering themselves unviable targets; even your most hardened AH gunner isn't going to follow them into a civilian-packed area once the attack has ceased.
I remember being told that a lot of old MANPADS kept by pro-Taliban forces are never considered for use as they're one shot weapons, and once used, the owner loses the bragging rights of having such a weapon. Perhaps the possibility that they'll take down a Prince means more will be tempted to pull them out?
Plus, if there are any arms being supplied by other nations, surey the chance to kill Harry would mean they might add a few MANPADS to their deliveries?