You're assuming that the source of the leak was the Bush Administration. The breadth of the subpoena net could cast doubt on that assumption. At any rate, it seems clear that the "leak" (or leaks) were passed out pretty widely, and I'm guessing over a long period of time.
I'd be really interested to know how many of the subpoena'd journalists knew Wilson/Plame on a social level. I'm guessing it was more than one of them... and that helps to explain why it was supposedly "common knowledge" that Ms. Plame was allegedly an undercover agent.
As it happens, I believe that Ms. Plame's role in the selection of Joe Wilson for his trip is actually quite relevant. My wife has been known to volunteer me for things at church and such, but that's not the same as a wife recommending her (manifestly unqualified) husband to go on an extremely sensitive intel-gathering mission. There's something very smelly about that, and it merits investigation.
I am assuming that...because that's what Novak said. But he could be lying and the assumption could be wrong. Who know's for sure?
manifestly unqualified
This is just plain wrong. He was manifestly qualified, and, even so, those who sent him were not satisfied just hearing from him. They also got reports from our Ambassador from Niger and from a four-star General with extensive experience in Africa. The reports of the latter two have never been released but Wilson has said that the Ambassador agreed with him.