Susan Stamberg’s interview with Lawrence Summers  puts on view the kind of person that cannot conceive of personal failure. I don’t think he’s denying responsibility for his failure; he is simply unable to see it.
This characteristic is so common among leaders that it’s probably a requirement for success. Such people inspire loyalty just because they always see the bright side of every situation. They can persuade others that they’re on the side of right because they believe themselves to be so. When something goes well, it must be because of their actions; when something goes wrong, it must be someone else’s fault.
Their motivational ability follows from an inability to see their own flaws. In a sense one can’t blame them for not taking responsibility; personal failure is just not the truth as they see it.
Jeff Skilling of Enron fame is another recent example. A Wall Street Journal article  reports that Skilling believed that if he just told the "real" story of Enron, he'd be in no danger. This led him to providing prosecutors with pieces of information that they effectively used against him at the trial. He didn’t believe then, and doesn’t believe now, that he committed any crimes, even though a Houston jury convicted him of 19 counts, including conspiracy, fraud and insider trading.
The “little people” find it hypocritical when leaders insist that employees take responsibility for their actions, but then don’t hold themselves accountable. The beam in the CEO’s eye doesn’t prevent him from seeing the splinter in everyone else’s... But be gentle; how can it be hypocritical if the Chief Ego Officer truthfully doesn’t believe that they’ve done anything wrong?
 NPR Morning Edition, “Summers Looks Back at Harvard Presidency,” 29 June 2006
 John Emshwiller, The Wall Street Journal, “In New Interview, Skilling Says He Hurt Case by Speaking Up,” 17 June 2006