It looks to me as if the big winner in the Fallon firing (and even Steve Clemons says it is a firing) is Adm. Fallon's nominal subordinate Gen. David Petraeus. It didn't look good for Petraeus to have his boss on a different page; it revealed Petraeus's spin for what it was.
And it's important for Petraeus to look good: not primarily because he's at least a long-shot contender for the vice-presidential slot on the McCain ticket, but because Petraeus is the key to the administration's domestic strategy for the fall.
Bush desperately wants a Republican to succeed him, not just to avoid the visible repudiation but also to keep the scandals under the rug. The linchpin of the political strategy is to tar the Democrats as not just weak on defense but part of the Dolchstoßlegende (stab in the back) tendency. And the man who's going to do much of the heavy lifting for Bush is Petraeus, who's currently hoping to do another round of testimony on the Hill on or about 9/11/08 — just as the electoral season kicks into high gear.
(Why the Democrats would allow this testimony on such a charged date is beyond me, but there's no understanding the political death wishes and spinelessness of our Senators. They allowed it last year.)
[Update (3/12): I'm told this year's testimony is actually scheduled for April 8 and 9 — the dates that US forces took Baghdad and the Saddam statue came down. Another triumph of Democratic planing.]