Ackman and Icahn's IEP suffer losses after Hindenburg report.

Billionaire investor Bill Ackman has questioned the valuation of Carl Icahn's flagship firm, Icahn Enterprises, after it became the target of short-seller Hindenburg Research. Ackman noted that the company's premium had been sustained by a large dividend yield, which is generated by returning capital to outside shareholders, funded by the company selling stock to investors. Hindenburg has accused IEP of overvaluing its holdings and relying on a "Ponzi-like" structure to pay dividends. Shares in IEP have lost more than half their value so far this year.