Well, perhaps. Lincoln said you could fool everybody once, and somebody everytime, but not everybody everytime, IIRC. Maybe the WMD question belonged to the 1st case ?
The hard part with human intelligence is that it's always tainted, either by the agents' own interests or because of prejudice, or even because of CYA procedures. I suppose most prepare three assessments of any situation, and give to their political masters whichever they feel the political leaders want to hear.
What strikes me here is that Powell really was at the forefront of the WMD story, he defended the case talons and claws, and he probably is one of the most exposed people, should the WMD story prove false. So, I'm quite impressed at the risks he takes saying "I was misled, and thus I misled you". Would he take such risks if he had no serious reason to doubt the WMD story ? I know I wouldn't.
If you read David Kay's report, you'll see that there was indeed a WMD threat from Saddam.
Well, ask yourself why the administration STILL refuses to insist that there are AQ in Iraq, despite tons of evidence that they were there before we invaded and that they are certainly there now. Why? I think it has to do with "burden of proof" and the media. Anything short of a ballistic missile with Saddam's fingerprints on it and a chem/bio warhead is going to be dismissed as "not" a "WMD." I think this is an acknowledgment of the nature of the MEDIA rather than the nature of the EVIDENCE.
BTW, story out as we speak: Sarin gas bomb exploded today in Iraq. Hmmmm.