Presidential advisors should be able to keep secrets. But, attorneys don't reveal secrets on national television. Priests don't write newspaper op-ed pieces disclosing confessions they've heard. Condoleeza Rice has done both. A Presidential privilege isn't a privilege any more when the secret is out.
Ms. Rice is wrong about the precedent's she'd set if she testified before Congress. Carter's Zbigniew Brzezinski, Clinton's Sandy Berger, and Nixon's John Dean and John Ehrlichman all did so. No one is threatening any subpoenas here. Congress is just asking for Ms. Rice's testimony.
The only reason for Ms. Rice to be willing to talk on television, but not in front of Congress is her fear of going under oath where she could be punished for perjury. Unthinkable? Two words: Oliver North. If Ms. Rice is telling the truth, she needs to testify under oath. If she won't, we shouldn't believe her.