So now the leadership lineup, in order, is Pelosi-Hoyer-Clyburn-Emanuel -- a fairly fractious crew. One could be of two minds about this. On the one hand, a fairly fractious leadership group might lead to a fractious caucus, creating trouble down the road. More optimistically, the caucus just is diverse in terms of ideologies, constituencies, and personal loyalties. Nevertheless, it's in everyone's interest to try and find ways to hang together, rather than separately. Arguably, a leadership team that reflects cleavages that would exist one way or another will be better able to mediate those cleavages and forge a reasonable path forward. After all, though the Pelosi/Hoyer 1/2 punch didn't look intuitive on paper, it was actually very effective during the minority period.
UPDATE: For a more "sky is falling" take on Pelosi's missteps here, see Crowley, Zengerle, and Orr. Last night, I was very pessimistic about this (foreseeable) outcome, but Rosenfeld sort of talked me out of being so sure about that. For one thing, as Ezra notes more-or-less this exact same thing happened to the GOP after their 1994 win and the Republican caucus survived and prospered.
I guess the question becomes: Apart from Pelosi looking bad, what concrete problematic things are going to follow from this. In the nightmare scenario, Hoyer decides that if Dems face setbacks in 2008, people will blame Pelosi opening the door for her to be dumped and him to take over as the #1 Democrat and so he deliberately engineers political problems for the Democratic caucus. That, however, strikes me as a more-than-a-bit outlandish scenario. It's a lot better to be #2 guy in the majority than the #1 guy in the minority so you'd need to be pretty crazy to deliberately risk electoral defeat. As I said above, the Pelosi-Hoyer relationship was already very tense before the election and, in practice, there didn't seem to be big blowups or obvious problems.