NEW YORK ( TheStreet) -- With a nickname like "the Oracle of Omaha," it is possible to forget that Warren Buffett has made his fair share of mistakes during his multi-decade investing career. In this year's Berkshire Hathaway ( BRK.A) letter to shareholders, however, the billionaire investor took time to present some of his most recent flubs, reminding investors, fans, and market commentators that not even the most famous and successful of investors are immune to the market's challenges.Given his success and charisma, it is not surprising that Buffett's highlights are well documented. In addition to his successes, though, fans and followers also keep close tabs on the investor's slip-ups. For example, many are well aware of the investor's past troubles with the airline industry. Although he has managed to successfully turn around NetJets in recent years, the staggering loss he was forced to write off from his bad bet on U.S. Airways remains a smudge on his record.