The idea came from Rep. Tancredo, who is advocating bombing Mecca, or at least threatening to bomb Mecca, as a retaliatory measure if Osama doesn't knock it off pretty soon.
As I asked before on the Jawa Report discussion: do the same folks advocate threatening the Islamic holy city of Jerusalem also? Why not? Is it because bombing Jerusalem would just make us more enemies? Is it because we know Osama would like nothing better than to watch us nuke Jerusalem and stir up those enemies? I submit that it's a little of both.
I can see the Islamist propaganda now: you think the war isn't really a war against Islam? If so, then why are the Americans calling to incinerate the Holy City of Mecca when they are supposedly friends with the Saudis? Don't fall for their lies! Stand up and defend Mecca!