It's up to the boards to hold CEOs responsible for their decisions by questioning them when warranted. Sadly, that didn't happen in the case of Lehman and AIG. In the case of both, it cost them the companies. In this environment, even the most gilded companies' CEOs -- such as Lloyd Blankfein of Goldman Sachs ( GS) and John Mack of Morgan Stanley ( MS) -- need to be questioned by their boards. Worst-case scenarios must be discussed and preparations made. Just because a CEO has a long tenure at a company and holds the title of chief executive doesn't mean he or she will fail; it simply means he or she needs to be on guard against "conventional wisdom." Conventional wisdom a few months ago was that Lehman was no Bear Stearns. Wachovia's ( WB) new CEO, Robert Steel, appears to be using his financial industry experience (he formerly served as head of equities at Goldman and undersecretary of the Treasury), as well as his lack of Wachovia tenure, to make quick moves in downsizing and separating the good and bad aspects of the bank in his first couple of months on the job. It warrants watching if he can be successful in doing what's needed at that bank in comparison to Thain's moves at Merrill. Vikram Pandit, the CEO of Citigroup ( C), deserves a lot of scrutiny. He came to Citi after his Old Lane hedge fund was acquired. So far, he has done little to separate himself from the model that Sandy Weill built and for which Chuck Prince acted as caretaker. Will Pandit be just another caretaker? How will Citigroup be defined under his tenure? We have yet to find out. In the meantime, the company's stock drifts lower with the industry, and Citigroup continues to pay a dividend it can't afford. There is no urgent capital-raising needed yet, but Pandit needs to have the pressure kept on him. In these difficult times, all CEOs and directors must come to work each day with fresh eyes to confront the problems they face. No matter how much past success they've achieved, no matter how esteemed these CEOs are, Lehman and AIG have taught us how easily everything that it took generations to build can be lost. There, but for the grace of God, go I.