From the comments

From Ezra's comments, this is ctown_woody:

Ezra,
To what extent is the Fed worried about making a visible commitment and failing? If Tyler Cowen and others are right that this slump is the end of family-deficit spending, it is quite conceivable that the Fed will fail to deliver that which it promises to deliver. At that point, the institutional players in the Fed will have lost credibility, which would lead to a lose of independence from politics.
So, to what extent is the Fed acting like Peter LaFleur from Dodgeball, "If you never try anything, you'll never fail"?