Almost a decade after Bitcoin was invented, the true identity of its creator - the pseudonymous Satoshi Nakamoto - is still unknown. But while its founder may remain a mystery, his or her vision for Bitcoin is not.

Nakamoto’s original White Paper, published in 2008, describes Bitcoin as “a peer-to-peer electronic cash system”, an “electronic coin” that would replace money transfers that are currently controlled by the financial system, and which would be almost immune to fraud.

Whoever Satoshi Nakamoto is - indeed, if they are even alive - the stash of Bitcoins the individual accumulated in its early days are now worth billions of dollars. But even as Bitcoin continues to break price records on an almost-daily basis, critics say it has strayed far from its original vision. The cryptocurrency (many disagree with the word itself) has proved to have almost no utility as a method of exchange.

Bitcoin has been dismissed as a commodity, not a currency, for years but there have still been plenty of opportunities to spend it. Expedia, Microsoft and Virgin Galactic have been among those willing to accept the digital currency.

But the frenzied interest of recent weeks has made things more difficult. This week one of the biggest supporters of cryptocurrency payments, the online video games seller Steam, announced that it would stop taking payments in Bitcoin. Valve, the service’s owner, said it had become “untenable”, owing both to its extreme volatility and the rising costs of using the network.