Cryptocurrencies are no different in that regard.

The maximum amount of each cryptocurrency is hardcoded into their design, but nothing stops people from "printing" new cryptocurrencies. There's bitcoin, litecoin, peercoin, darkcoin, namecoin, primecoin, and of course dogecoin... Gimme a few hours and I could cook up xiphiascoin in your honor.

And when something happens that makes people migrate en masse from one *coin to another (perhaps a security flaw in the reference implementation), you might wake up to find that your old coins are now worth less than a Zimbabwe dollar.