Mr. Buffett has long bragged about how thoroughly he conducts due diligence before making an acquisition. He's been doing that so long that he probably has shorthand rules and heuristics that help him focus on the value of a good deal. The problem with old habits is that they can breed laziness, especially when they allow you to develop blind spots in your inner circle. Trust is the ultimate shortcut. When you trust someone, you tend not to second-guess their agenda or even look into their recent past.
Warren Buffett trusted David Sokol and was betrayed. Here's hoping the Oracle of Omaha doesn't wait too long to find another heir apparent. I'm certainly available to fill those shoes if needed.
Full disclosure: No position in Berkshire Hathaway.