Bitcoin (and other virtual currencies) have the potential to revolutionize the way that payments are processed, but only if they become ubiquitous. This Article argues that if virtual currencies are used at that scale, it would pose threats to the stability of the financial system – threats that have been largely unexplored to date. Such threats will arise because the ability of a virtual currency to function as money is very fragile – Bitcoin can remain money only for so long as people have confidence that bitcoins will be readily accepted by others as a means of payment. Unlike the U.S. dollar, which is backed by both a national government and a central bank, and the euro, which is at least backed by a central bank, there is no institution that can shore up confidence in Bitcoin (or any other virtual currency) in the event of a panic. This Article explores some regulatory measures that could help address the systemic risks posed by virtual currencies, but argues that the best way to contain those risks is for regulated institutions to outcompete virtual currencies by offering better payment services, thus consigning virtual currencies to a niche role in the economy. This Article therefore concludes by exploring how the distributed ledger technology pioneered by Bitcoin could be adapted to allow regulated entities to provide vastly more efficient payment services for sovereign currency-denominated transactions, while at the same time seeking to avoid concentrating the provision of those payment services within “too big to fail” banks.