Kyle Bass, founder and principal of Hayman Capital Management, says he believes Herbalife is not a ponzi scheme and is a legitimate business model on an interview with CNBC. He even goes as far as saying they've had one of their own traders sign up with Herbalife to gain an understanding of the model to make sure it's legitimate.
Bass became well-known after successfully predicting and benefitting from the subprime mortgage crisis by purchasing credit default swaps on subprime securities issued by various investment banks (similar to shorting the bonds).