One of the interesting threads in the attorney scandal is that White House officials did lots of their communicating via Republican National Committee e-mails rather than White House e-mails. E.g., there is a report that Rove does 95% of his e-mailing via the RNC address.
Trivial though this may sound, there is also reason to believe that a lot of this has been done deliberately to evade legal requirements pertaining to recording and retention of official communications.
How does this play into the executive privilege claims? The natural analogy is attorney-client privilege, which is easily blown by the parties who want to claim it in various circumstances where they failed to treat a communication as confidential and as within the attorney-client relationship. Plus, there is no privilege where the attorney is providing not legal advice but something else (e.g., investment or tax accounting advice). It's a truism among knowledgeable practitioners that far less is actually covered by the privilege than lawyers tend to think while they are going about their daily business.
Obviously, there is next to no legal precedent on the boundaries of executive privilege, compared to the centuries of cases et al regarding the attorney-client privilege. But the privileges are similarly motivated cousins, and analogies from the latter are by no means irrelevant to thinking about the former. And if you think there's a special public purpose to letting the president get confidential advice, there's also a special public purpose to preventing him from evading oversight.
The easy and obvious point is that anything Rove sent out in an e-mail from his RNC address is not privileged. Call it a foot fault, if you like, but that's just tough, and doesn't call for sympathy given his likely unclean hands in using the RNC address.
A further interesting question is the extent to which using RNC e-mails to communicate stuff about meetings with Bush et al should be viewed as a further waiver of other executive privilege claims, at the limit on everything pertaining to the meetings and topics discussed in the RNC e-mails. On this point I would have to defer to those more knowledgeable than I am about how the attorney-client privilege is interpreted and applied.
But it strikes me as possible that we have an argument for a total waiver situation, even leaving aside the point that the attorney-client privilege does not cover criminal activity (relevant here given the strong inference of obstruction of justice as the cornerstone of the entire caper).
I certainly hope these arguments will be fully raised and vetted both in public debate and in any litigation on Bush's privilege claims.