Remember when Chimpy promised the people that if anyone in his administration had been involved in blowing the cover of Valerie Plame they would no longer work in the (our) White House? Yet now that the evidence is out clearly marking Libby and Rove as the actors-in-chief, Libby's boss is praising him for his service to the country and Rove is still in place.
I postulate a simple reason for this. Both Cheney and Chimpy knew and approved.
Gotta love simplicity. Cuts right through the spin, doesn't it?