(Wired) Mark Karpeles is the man who built the world’s largest bitcoin exchange. But now that the digital currency is reaching the mainstream, his success may slip through his fingers.

In 2011, Karpeles bought a fledgling website called Mt. Gox. Founded a few years earlier by an unemployed software hacker named Jed McCaleb, the site was originally an online marketplace where people could buy and sell cards for Magic: The Gathering, a weirdly addictive trading card game. Mt. Gox was short for “Magic: The Gathering Online Exchange.” But then McCaleb turned it into a website where people could exchange cash for bitcoins, a digital currency that had only just found its way onto the internet, and just as the exchange started to take off, he sold it to Karpeles.

Under Karpeles, Mt. Gox evolved into a reliable marketplace for buying and selling bitcoins, now the world’s most popular digital currency. By one estimate, Karpeles has made over $8 million plus 345,000 bitcoins (at current rates: $86 million) swapping bitcoins for dollars and yen and other federal currencies. But much like McCaleb, he’s a hacker rather than a businessman. He seems more at home talking about IRC than the IMF, and as Mt. Gox has grown, he and his company have found it difficult to deal with the realities of the financial world.

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