Thanks to a savvy investment made by Warren Buffett several years ago, Berkshire Hathaway (NYSE: BRK-A) (NYSE: BRK-B) recently became the largest shareholder in Bank of America (NYSE: BAC). The Buffett-led conglomerate owns 700 million shares of the banking giant. Let’s look at the percentage of Bank of America that Buffett owns, and review how the Oracle of Omaha came to be Bank of America’s biggest investor.