I have noticed that, but I have also noticed that it is the CIA which confirms their authenticity, and which has its own motivations, which are not necessarily identical to those of the administration.
Yes, it's a perfect bank shot for GWB. He uses the guys who hate him in the CIA to confirm the authenticity of bogus OBL tapes. It's a beautiful thing!
The CIA guys were willing to do it so the Dems could ridicule GWB for not getting OBL.
W didn't care 'cause he got the larger advantage of keeping peoples' attention focused on th WOT.