Today millions of Americans will scramble to acquire a piece of Warren Buffett, as his Berkshire Hathaway Inc. goes mainstream to join Standard & Poor’s 500-stock index. “More than $1 trillion of investor money directly tracks the index. The result is a scramble for Berkshire shares by index funds that, by one estimate, will reach $14 billion of buying. This further exposes Berkshire stock to the stratagems of fast-moving traders, a brand of investor anathema to Mr. Buffett's general buy-and-hold approach. Small-time investors, meanwhile, will finally be getting a piece of Mr. Buffett just as uncertainty builds about the future of his $178 billion conglomerate, which is one of the largest public companies in the U.S., selling everything from insurance to underwear. The 79-year-old Mr. Buffett is entering the twilight of his career, and little is known about his succession plans, other than that he has placed the name of his replacement in an envelope he keeps in his office. Yet small investors are likely soon to have billions of dollars more in Berkshire stock, thanks both to its entry into the index and to a recent stock split.”