FOR fans of bitcoin, a digital currency, the year got off to a volatile start. On January 5th one bitcoin changed hands for nearly $1,150—almost as much as the record set three years ago. It has since dropped by 33%. Elsewhere in the land of monetary bits, things move more slowly but trouble is brewing: a potential patent war looms over the blockchain, a distributed ledger that authenticates and records every bitcoin transaction. Heated fights over intellectual property are nothing new in promising technology markets.