I'm not sure if Pershing Square's Bill Ackman will win in his quest to bring down multi-level marketing giant Herbalife Ltd. (NYSE: HLF ). Given the recent rally, activist investor Carl Icahn might be successful in forcing the "mother of all short squeezes." Neither result would surprise me. But, regardless of what ultimately happens to shares of Herbalife Ltd. (NYSE:HLF), the MLM business is itself fundamentally flawed. Is there another business model (not just a business, but the entire model ) that has received as much scrutiny as MLM? Given the fine line MLM businesses must walk to stay on the right side of the law, I'm not sure why anyone would invest in a company like Herbalife Ltd. (NYSE:HLF), or for that matter, other MLMs such as USANA Health Sciences, Inc. (NYSE: USNA ) and Nu Skin Enterprises, Inc. (NYSE: NUS ). Criticisms of MLM MLM critics are easy to find.