A money changer sits behind piles of banknotes in Hargeisa in Somaliland, an autonomous, relatively peaceful region in northern Somalia. The self-declared nation of Somaliland, like Somalia itself, lacks a formal banking system, and residents rely on hawaladars to receive money from abroad. Simon Maina/AFP/Getty Images hide caption

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Even some euro bank notes may need a good scrubbing. Like dollar bills, these notes are made from cotton and they harbor an array of bacteria. Thomas Leuthard/The Preiser Project/Flickr hide caption

itoggle caption Thomas Leuthard/The Preiser Project/Flickr

Several Silicon Valley entrepreneurs are developing services that manage consumers' investment portfolios with algorithms rather than people. iStockphoto hide caption

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An image depicts the SatoshiDice website, which exclusively uses Bitcoin, not dollars, for gambling. NPR hide caption

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