Billionaires piled into the largest company in the world, nearly offsetting Buffett's massive sale.Warren Buffett is considered by many as one of the greatest investors of all time. The longevity of his success is remarkable, starting as a public investor in the 1950s after establishing his own investment partnership. As Chairman and CEO of Berkshire Hathaway (BRK.A 1.85%) (BRK.B 1.61%), Buffett is in charge of managing the bulk of the conglomerate's equity portfolio. And he's done so with incredible result ...