Part of your point here might have been that there was no underlying crime to investigate in this case. If that was your point I think that that is probably not correct.
Let me qualify my earlier comment; I won't contend, at this point in time, that no violation of the law occurred. I will, however, contend, that no violation of the law has (yet) been shown to have occurred, and I'm inclined to think--on the basis of my personal experience working as a flunkey in a prosecutorial organization--that two years should be more than enough time to establish whether or not the identification of Valerie Plame as an employee of the CIA actually constituted a violation of the law. Based on what I've read, it appears that Plame does not meet the definition of "covert agent" set out in the Intelligence Identities Protection Act of 1982, since she had not worked outside the US in the five years prior to July 2003. Now, I might be misinformed on this point, but I would think that two years would be enough time for a special prosecutor to establish this one way or the other. How hard can it be to find the appropriate people at Langley, place a copy of the Act in front of them and ask "Did Valerie Plame meet the definition of 'covert operative' as of July 2003, yes or no?"?
In that regard, there is what I consider to be an extremely disturbing element in prosecutorial culture in the US, which is a tendency to first identify a suspect and only then go looking for something to nail him on, and keeping on trolling until something is found, no matter how trivial it would be if taken by itself. I would say this started with the conviction of Al Capone for tax evasion, the only thing the feds could actually pin on him. Now, I understand that in the case of organized crime bosses, this may be the only practical approach available, but I think such an approach should be used sparingly, not as matter of routine. Unfortunately, as I understand it, Fitzgerald made his mark nailing organized crime bosses, and I suspect that the tendency to employ this approach may be particularly strong in him.
As for the CIA, I suspect the culture towards secrecy may be a lot stronger than is actually supported by the law. Somone on another board told me a fellow student of his did an internship at Langley one summer; this guy didn't do anything remotely covert, but everyone around him was officially discouraged from mentioning his involvement with the Agency. Intelligence agencies love to keep things secret, and I bet the CIA's pretty annoyed at Plame's status being exposed, but it's not the CIA's call whether or not that should illegal.
And yeah, the White House seems to have been hell-bent on covering up who leaked Plame's name to the press, but as you yourself say, Dave, that's because the leak was arguably a serious breach of public trust, whether it was illegal or not.