Buffett's Heir Apparent Resigns Under Cloud David Sokol steps down amid questions over stock buy By Rob Quinn, Newser Staff Posted Mar 30, 2011 11:00 PM CDT 4 comments Comments David Sokol, in Omaha, Neb. Sokol, once thought to be a possible successor to investor Warren Buffett, has resigned. (AP Photo/Nati Harnik, File) (Newser) – A Berkshire Hathaway executive once seen as the likeliest successor to billionaire investor Warren Buffett has abruptly resigned. David Sokol—who ran Berkshire subsidiaries including MidAmerican Energy and NetJets—says he is quitting to devote more time to philanthropy. His resignation, however, comes amid controversy over Sokol's acquisition of thousands of shares in a company soon before Berkshire entered talks to buy the company at his suggestion, the New York Times notes. "Neither Dave nor I feel his Lubrizol purchases were in any way unlawful,” Buffett said in a statement. “He has told me that they were not a factor in his decision to resign.” Buffett says he learned earlier this month that Sokol bought almost 100,000 shares in chemical company Lubrizol a week before he recommended that Berkshire make an offer for the company. It's unclear whether Sokol will face any legal repercussions over the deal.