This morning’s Observer column.

Among the many unpleasant discoveries made by those who stashed their cash in Cypriot banks is that the island’s government could stop them moving their money elsewhere. Capital controls are supposed to be a thing of the past, a figment of the pre-globalised world. But it turns out that when banks are threatened, the gloves come off.

One of the side-effects of this rude awakening seems to have been a surge of interest in a virtual currency called Bitcoin. At any rate, the price of a single Bitcoin reached $147 at one point last week…