If I were trying to win the nomination in 2008 as a well known politician, I would not want to get involved in this. I would understand if another candidate retaliated to this....but that means Hillary suspects that Dean already has a favorite for '08. Unless it's himself (which I don't think it would be) I think this sort of meddling is bad news.
It portends that there's going to be a split in '08 between Deaniacs and Clintonistas. So even if we make gains elsewhere, we could still lose to a lightweight Republican for President. My guess is though if Dean ran as an independent he would do better than Hillary.
FYI: I tend to think that if this happens and we get stuck with Mitt Romney for 4 years, the obvious stone cold lock pick in '12 is Spitzer (perhaps with Obama as his VP). But I also think America in 2012 will be a lot more cognizant of "liberal" ideas because of what's going to happen between then and now in terms of foreign policy, economic policy, and demographics.