With regard to the question of why Judith Miller might be important to the investigation - in my first post on page one of this thread, I wrote: "The question of who leaked to the leakers may end up being just as interesting." I think it's possible - maybe even likely - that Karl Rove had never heard of or paid much attention to Joseph Wilson, let alone his CIA agent wife, until Wilson went public with the story about his Niger trip. Yet, within a week or so of that, Rove was apparently helping head up a campaign to discredit Wilson and Plame, including at one point telling Chris Matthews that Wilson's wife was "fair game." What went on in the interim? Today's Washington Post article has an intriguing quote along those lines: Remember, Miller was a primary conduit for the false WMD information being put out by Chalabi and his friends in the Bush administration; in this role, she would have learned a lot of interesting facts about the various players in the internal struggles over pre-war intelligence. So, it's conceivable that the investigation is focusing on Miller not just as a recipient of a leak, but also as a (possibly unwitting) participant in that leak.
Following up - here's an interesting blog post that came out few days ago, speculating on the theory that Judith Miller is involved in this case in some capacity beyond being a recipient of the leak. Pretty impressive guesswork, since this came out several days before the WaPo piece that mentioned the possibility that investigators might be looking at reporters giving info to the administration. http://www.needlenose.com/node/view/1592 As evidence, the author points to another Washington Post article, from February, that states that investigators want information on a conversation between Judith Miller and an unnamed government official on or about July 6 2003. That was the same day that Wilson's story first went public - it seems unlikely that the official push-back against Wilson and his wife would have started that quickly.
actual bar conversation: DJP: Well, both Lil Kim and Judith Miller essentially did the same stupid thing. On purpose they made **** up and exaggerated it to draw the spotlight for professional and personal gain - whether it was an imagined hiphop slight or WMD stories full of lies. Friend: "Yeah, but Lil Kim only caused one n**** to get shot"