There are more means of personal expression these days than at any other time in history, but whether you choose message boards, graffiti, tattoos or even traditional artistic mediums, it's always more fun if there's an element of danger. One of the most cost-effective forms of dangerous personal expression -- that's just as illegal as graffiti -- is currency defacing.In a world where a $10,000,000 bill exists, it's clear money is worth less than the paper it's printed on. This makes the canv