FORTUNE — The year didn’t start off great for David Einhorn. But things seem to be turning around for the hedge fund manager.
First of all, Einhorn’s deal to buy a portion of the Mets fell apart in late 2011. Then in late January, the hedge fund manager, who is famous for predicting Lehman Brothers’ demise, and his firm Greenlight Capital were fined $11.2 million by the U.K.’s financial services authority for trading on information Einhorn got in a private call with the management of British pub operator Punch Taverns.
This week, though, has been pretty good to Einhorn. On Tuesday, the hedge fund manager showed up on a public conference call with the management of nutritional supplements company Herbalife (HLF) and asked a few skeptical questions. The stock nearly immediately lost 20% of its value. Clearly, when Einhorn talks the market still listens. On top of that the shares of Green Mountain Coffee (GMCR), which Einhorn has been betting against for at least a year, fell more than 40% after the company announced on Wednesday that it had missed earnings expectations in its fiscal second quarter. The coffee company’s shares may have more to drop. Then on Thursday, Einhorn took on Ben Bernanke, writing a story for the Huffington Post calling on Ben Bernanke to stop handing out the “jelly donuts.” The Fed’s low interest rate policy, Einhorn said, is no longer helping the economy.
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In general, Einhorn’s Greenlight, which is a so-called long-short fund because he buys stocks as well as bets against them, appears to be doing well this year, after a somewhat lackluster 2011. The fund was up just 2.9% last year, which was better than the market, but not by much. The fund’s biggest publicly disclosed holding is Apple (AAPL). The computer company’s shares are up 44% this year. Another good call: He upped his investment in General Motors (GM) in the fourth quarter. So far the bet has paid off. The car company’s stock is up 22% this year.
Einhorn has had some swings-and-misses as well. Greenlight has a $180 million stake in Best Buy. But shares of the electronic retailer, which is struggling to compete with Amazon and Apple, are down nearly 8% this year. Overall, though, it’s been a good year for Einhorn. Based on the holdings it has disclosed publicly, Greenlight is up 21% so far this year, according to hedge fund tracking site Insider Monkey.
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It’s not clear Einhorn has already placed his bets against Herbalife, but it seems likely he would do so before tipping his hand, even slightly. Einhorn only asked three questions on the conference call, so it’s not clear why he thinks the company’s shares will fall. But Tracy Coenen, a forensic accountant, who has been following Herbalife for a few years, says that from Einhorn’s questions it appears he is concerned about Herbalife’s growth. Herbalife’s business model is similar to Avon. It sells its products in bulk to individuals who then resell the products to other people. Herbalife “salespeople” can also make money recruiting others to sell Herbalife products. Coenen says that most companies like Herbalife lose 60%-90% of their sales people a year. So the business model is based on constant recruitment. Recently, Herbalife stopped disclosing how many of its salespeople solely make their money from recruitment, something it traditionally told investors. On the conference call, Einhorn asked why it had changed its policy. The company’s CEO responded that he and the other executives didn’t think it was a valuable metric. But after the conference call, the company disclosed on its website that its percentage of salepeople who were recruiters had dropped to 12%. That number was in the 20s a few years ago.
“Herbalife’s growth is slowing, if not stopped all together,” says Coenen. “I think Einhorn knows a lot more about this company than he is letting on.”