Crypto currencies can exist for those who want them, I don't see any reason to block them beyond ponzi scheme and marketing issues - similar to stock issues. So

Crypto currencies can exist for those who want them, I don't see any reason to block them beyond ponzi scheme and marketing issues - similar to stock issues. So probably they need some regulation to not defraud unwitting people. Bitcoin is not an alternative to Euros. That is the whole point. If you switched all euros to bitcoins and asked people to trade those, the economy would collapse as no one would want to trade their bitcoins because mathematically, they increase in value due to the limited issuance of them. Without modest inflation, the economy cannot grow as no one would spend money for investment purposes.