Warren Buffett has retired as the CEO of Berkshire Hathaway Inc., marking the end of his six-decade-long tenure. Greg Abel, his successor, took charge on the first day of the new year, stepping into a role fraught with challenges. What Happened: Abel’s key responsibility will be the effective allocation of Berkshire’s burgeoning cash reserves, which recently crossed the $350 billion mark. This amount surpasses the market values of Home Depot Inc. (NYSE:HD), Procter & Gamble Co. (NYSE:PG), and General Electr ...