Greg Abel faces the challenge of taking over Berkshire Hathaway from the legendary Warren Buffett later this week.Many regard Buffett as the world’s greatest investor after he grew Berkshire from a struggling New England textile mill that he starting buying up for $7.60 a share in 1962, to the massive conglomerate it is today with shares that go for more than $750,000 a pop. Buffett’s personal fortune of Berkshire stock is worth roughly $150 billion even after giving away more than $60 billion o...