Billionaires list includes top political donors

The annual Forbes list of the world's top billionaires should look familiar to American political junkies.

Businessmen Charles and David Koch, New York City Mayor Michael Bloomberg and casino developer Sheldon Adelson — who put some of their vast personal fortunes on the line in the 2012 elections — are among the world's top 20 billionaires, according to the magazine's list.

The Koch brothers, who are each worth an estimated $34 billion, rank 6th on the list because of the wealth accumulated from the oil-refining business founded by their father. They pumped millions of dollars last year into conservative causes, including Americans for Prosperity, which was behind many ads criticizing President Obama. David Koch helped raise money for Mitt Romney's presidential campaign and was a delegate to the Republican National Convention in Tampa. Read more >>