The biggest name in investing is making what he calls an "all-in wager" on the U.S. economy -- $34 billion to own a railroad that hauls everything from corn to cars across the country. The acquisition of Burlington Northern Santa Fe, the nation's second-largest railroad, would be the biggest ever for Warren Buffett's Berkshire Hathaway investment company. It's a natural fit for the Oracle of Omaha, a city with a special place in railroad history. It was the starting point for the westward push of the transcontinental railroad. Today, Omaha is the headquarters of Union Pacific, and Burlington Northern trains rumble through. In a statement, Buffett, whose investing decisions are carefully scrutinized by the world of finance, voiced...