Rubin, who previously served as Secretary of the US Treasury and head of Goldman Sachs, is widely reputed to be one of the savviest executives around. He is also famous for not making decisions until he has to, because situations change and more facts tend to emerge. After analyzing his situation, Rubin came to the conclusion that he could not jointly fulfill his obligations as chairman of the Executive Committee of the Board at Citigroup, and his role as Board member at Ford. In a letter to Ford’s Chairman and CEO, Rubin wrote that Citigroup’s “multifaceted relationship with Ford could raise a question whether my relationship with Ford and Citigroup creates an appearance of conflict.”

Most corporate codes of conduct caution against situations that create a conflict of interest, or even the appearance of one. Most of these Codes go on to counsel disclosure of the potential conflict as a first course of action, with recusal from the situation as the next step. Rubin’s resignation indicates that he does not believe recusal from decisions involving Citigroup is a viable option any longer. “Although no conflict currently exists and while I would have liked to remain involved, I have with great regret concluded that I should resign from the board at this time.”

Is Rubin’s resignation an isolated event, stemming from Ford’s well known difficulties and the high probability of significant financial restructurings in the next few months? Perhaps. But I think Rubin has correctly read the corporate governance tea leaves, and we will see more departures of bankers, attorneys, suppliers and customers from corporate Boards in the next year.

Whether this is an advance for American corporations is harder to predict. Rubin was one of the bright lights on Ford’s board, and Ford’s shareholders will miss his high-beam intensity as the company maneuvers the dark and dangerous road ahead. Disclosure, transparency and recusal may have served Ford better.