Hubris has driven William Ackman in his battle against Herbalife. His $1 billion short position was built on the assumption that regulators would immediately step in and shut down the company, sending shares to zero. Five hundred million dollars, two years and tens of thousands of man-hours later, Mr. Ackman has hardly reaped the fruits of his labor. Instead, he is sitting on security losses well in excess of $500 million. Mr. Ackman's three and a half hour presentation last week, which he sold as a "death blow" and the "most important of his career", supremely backfired. In a punishing referendum, Herbalife's stock price rose throughout the talk, climbing more than 25 percent by the end of the trading day. Mr. Ackman's career in finance is hardly over. But he will never forget "the most important presentation of [his] career." Perhaps, once this experience has marinated for awhile, he'll approach future investment decisions with the sobriety and analytical rigor for which he was once so well known.

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