An American billionaire investor with reputation for being a shrewd activist investor. Icahn is known for buying large amounts of stock in a specific company, and then pressuring the company to make significant changes to increase its value. Taobiz explains Carl Icahn As of 2008, Icahn's net worth was estimated to be in the range of $14 billion, placing him in top 50 of the richest people in the world. Some of his best known stock market activities are his effort in 2000 to get RJR Nabisco to spin off its food segment from its tobacco business, and his 2008 investment in Yahoo and the opinion that existing management had mishandled its negotiations of a possible combination with Microsoft.