  Bitcoins have emerged as a possible competitor to usual currencies, but other
crypto-currencies have likewise appeared as competitors to the Bitcoin
currency. The expanding market of crypto-currencies now involves capital
equivalent to $10^{10}$ US Dollars, providing academia with an unusual
opportunity to study the emergence of value. Here we show that the Bitcoin
currency in itself is not special, but may rather be understood as the
contemporary dominating crypto-currency that may well be replaced by other
currencies. We suggest that perception of value in a social system is generated
by a voter-like dynamics, where fashions form and disperse even in the case
where information is only exchanged on a pairwise basis between agents.
