The Saudis fund terrorism to get the terrorists out of Saudi Arabia - they would much prefer their home-grown radicals concentrate on a Medrassas in Iraq than overthrough the House of Saud.
I the CoG is Saudi money, then the Critical Vulnerability the West's tolerance for the Hause of Saud.
Mmmmm, I do have to agree that shuting off the terorists access to funds would really cramp their style quite a lot.