Are Bitcoins the Criminal's Best Friend?

Until very recently, the virtual currency known as bitcoins could be mistaken for just another Internet fad (the Winkelvoss twins of Facebook fame even had a role). But when federal law enforcement closed the "Silk Road," the wildly popular online illegal-drug emporium that used Bitcoin as a medium of exchange, politicians and policy makers took notice. Criminals, it turns out, really like bitcoins, which can be exchanged for nefarious purposes on the "Dark Web," with complete anonymity and, it seems, impunity.

The shift to a virtual currency signals a huge -- and worrisome -- shift in behavior for criminals, who for decades have favored cold, hard cash, with the dollar the preferred medium of exchange. Just how alarmed we should be is one of the topics of a hearing today in the Senate Committee on Homeland Security and Governmental Affairs.