You probably learned in American history class about the "shot heard 'round the world," but what about the short heard 'round the world? Let the textbooks duly note that on Dec. 19, 2012, Bill Ackman and his Pershing Square Capital Management hedge fund fired off the short that rocked the investing world -- a $1 billion bet against weight loss and nutritional supplement seller Herbalife Ltd. (NYSE:HLF) . This massive short-sell also set off what has now become a full-blown war of the hedge funds. Let's look at the history and potential future of this epic battle over Herbalife.

Mustering the troops This war officially started on Dec. 19 with Bill Ackman's allegations that Herbalife Ltd. (NYSE:HLF) was a "pyramid scheme," but the battle had actually quietly started months before when he first began shorting the stock. Shares of the company dropped nearly 15% soon after his public announcement disparaging Herbalife's business model. Herbalife CEO Michael Johnson took to the airwaves later in the day to vehemently deny Ackman's charges, accusing the hedge fund manager of "blatant market manipulation."

Ackman followed up on Dec. 20 with a presentation detailing his specific issues related to Herbalife. The next day, the company announced that it would respond to all of the allegations with an analyst day the week of Jan. 7. This event was ultimately held on Jan. 10.

In an intriguing twist, the skirmish between Pershing Square and Herbalife Ltd. (NYSE:HLF) erupted into a much larger conflict. Robert Chapman with hedge fund Chapman Capital Partners went public with his skepticism about Ackman's position. Daniel Loeb's hedge fund, Third Point LLC, bought an 8.2% stake in Herbalife. Loeb directly challenged Ackman's assertions, calling them "preposterous."

Bronte Capital's John Hempton, no fan of Herbalife, stated that Ackman "did not check the facts." Just this week, billionaire Carl Icahn announced that he bought a small position in Herbalife. If Honey Boo Boo ran a hedge fund, she'd probably be taking sides as well.

Battle lines How does Bill Ackman back up his allegations that Herbalife Ltd. (NYSE:HLF) is a pyramid scheme? In a nutshell, he says that the company's distributors receive more money from recruiting other distributors than they do from selling Herbalife's products.

Ackman maintains that Herbalife prices its products to be much more expensive than rivals. His premise is that the company's intention is to inflate retail sales to look larger than recruiting rewards paid to distributors. He also says that Herbalife lowers its actual recruiting reward dollars by reflecting vacations and other promotions that are perks for top recruiters in the selling, general, and administration expenses line item.

The Pershing Square boss accuses Herbalife of selling "business opportunity" more than products. Of the products that Herbalife does sell, Ackman says that most of the sales are to distributors with few outside customers. He also states that Herbalife's growth numbers are misleading and unsustainable because they are based on a "pop and drop" approach that depends primarily on moving to new markets for growth to hide declines in established markets.

Herbalife Ltd. (NYSE:HLF) counters that Formula 1's price per serving is actually in the middle of major rivals' prices (although no response is given to overpricing allegations about its other products). The company points to what it perceives as several flaws in Ackman's argument about its financial reporting of sales information. Herbalife categorically denies that it pays distributors to recruit others.

Regarding Ackman's claim that there are few outside customers, Herbalife cites market research performed by Lieberman Research that found that 92% of the company's customers are outside of its distributor network. The company notes that this research showed that most distributors joined the network primarily to obtain discounts for their own consumption. Herbalife responds to the "pop and drop" accusations with the observation that only 8% of its 2012 sales as of September were from markets that the company entered less than 10 years ago.