The simple fact that the CIA Director George Tenet, did not know of Joe Wilson's trip to Niger in advance is a major scandal in itself. Here we have an issue that could be the difference between war and peace, and the CIA Director was not told of this adventure???
This trip to Niger that was arranged by Valerie Plame was an orchestrated attempt to undermine the Foreign Policy of this President and our Constitution clearly gives the President of the United States the power to decide what our foreign policy will be. A rogue element within the CIA obviously ignored this Constitutional power granted to the POTUS when they sent a former Ambassador to Niger to get the results they wanted in order to undermine this Presidents foreign policy.
This is how I see this whole deal
I have a different take on why Miller went to jail. First of all, Fitzgerald needed her testimony to prove that Libby had told her about Wilson's wife. He probably was also trying to get her to incriminate Cheney as well.
Additionally, an unstated reason for showing no leniency to Miller is that she accidentally tipped off the head of a charity that was funding Al Qaeda that Fitzgerald was going to raid their office the next day. The charity went to into overdrive destroying documents. Fitzgerald indicted the organizations leader but was not able to get a conviction. One of the biggest blemishes on his record.