Like Orin, I was quite skeptical when I heard that Bush Justice Department appointee Monica Goodling planned to invoke her Fifth Amendment rights against self-incrimination if called to testify about why the administration decided to remove several U.S. attorneys. Eric Muller is "disgust[ed]" by the Justice Department's actions, but nonetheless thinks she was justified. As he writes on Is that Legal?

The Fifth Amendment privilege protects not just the guilty, but also the innocent, who fear that even their entirely truthful responses might provide the government with incriminating evidence from their own mouths. (Ohio v. Reiner, 532 U.S. 17 (2001) (dictum).) "The privilege serves to protect the innocent who otherwise might be ensnared by ambiguous circumstances." (Slochower v. Bd. of Higher Ed. of the City of New York, 350 U.S. 551, 557-58 (1956).)

A careful defense lawyer would be especially justified in advising his or her client to consider taking the Fifth in a highly charged political environment such as the Senate Judiciary Committee's investigation into the firings of U.S. Attorneys and the alleged minimization (dare we say "cover-up?") of the role of the Attorney General and the White House in those firings. It is important to remember that "a witness innocent of wrongdoing may well refuse to answer a question not because he fears conviction, but because he fears unfounded prosecution, a risk which every one runs at all times, theoretically at least." (Lewis Mayers, Shall We Amend the Fifth Amendment? 4 (New York: Harper & Brothers, 1959).)

Both Orin and Eric know more about the right against self-incrimination than I do, so I'll defer to the two of them.