For me, we need to regulate digital currencies, especially bitcoin to fully make use of it as payment in online transactions. And so that, bitcoin and other cryptos will exist forever. Although it opposes its idea being a decentralized cryptocurrency, I believe we need to do this in order that bitcoin and other cryptos survive for long in the crypto or real world.
Yeah we need some assurance that our money will be safe everytime we invest or if it is being used to realize the project that we invested and will not go to the pocket of the CEO and team doing ICO projects. Aside from that government could watch over the market price movement so that it will not manipulated if there are manipulations and the government could identify people who are getting involve in cryptocurrency for national security. Aside from that government could watch over the market price movement so that it will not manipulated if there are manipulations and the government could identify people who are getting involve in cryptocurrency for national security.
I don't think that governments can stop the manipulations of crypto currencies even if they regulate it because Bitcoin is decentralized and it is created without anyone controlling it and it gives freedom for everyone that uses it. But the manipulation of this crypto currency is expected especially to those people or whales that have a huge amount of this currencies. 