No boss wants to be embarrassed, including a President. The 7-page questionnaire introduced by the Obama Administration for candidates is necessarily thorough. Those seeking to occupy cabinet level positions for the most powerful nation in the world should have no problem filling out a form, and be willing to answer in depth personal questions without fear of what may be revealed about them. If there are no skeletons in the closet, none can be discovered.
This is bigger than embarrassment for a candidate, one vouching like Rudolph Giuliani did for Kerik, or even a president nominating. 
America needs assurance that those holding highly responsible positions will do the right thing. “If only we had known” is the wail of those victimized by leaders harboring criminal, tyrannical, dishonest, negligent, or reckless intentions. When the powerful become notorious, a look back often reveals visible flaws of the heart. Finding trustworthy people likely to succeed means going beyond what anyone says about self ‘it means checking them out’. Since among the many highly qualified candidates there rests relatively few jobs, ethics can be a filter. All the knowledge and skills in the world in the hands of someone unwilling to do what is right is dangerous. The intense vetting that takes place for every government career employee placed under the wrong leadership can render an agency’s mission moot.
Not all failed nominations are failures. Success occurs on a journey to get the right person, when candidates are eliminated because derogatory information bearing on decision-making is identified before hire. Mistakes are different from intentional misdeeds; and every candidate for a sensitive position subject to a background investigation should examine self with an awareness of personal circumstance. Perhaps it is the honor of being selected that deludes some candidates into minimizing past deeds or the likelihood of detection by investigators. But doing right is the only ethically marketable guarantee when great opportunities come.
Even if your prospective boss is not the President of the United States, he or she wants to bet on a winner. The best way an employer can believe you are a sure thing is to dig into your past. It’s not being picky, ‘it’s being choosy’ and choosy bosses, choose predictable winners.