i think that bitcoin can challenge the value transfer of traditional fiat system but on the other hand, if the government is deciding to ban such digital currencies then it would boost the shadow usage of it and those who are using Bitcoins for legal activities would not use it in that case but those who are using Bitcoins for illegal use, would keep using Bitcoins under cover and I fear that the percentage will increase drastically if there is any wrong move by the government and Many government show their negative attitude towards Bitcoin and ban it in their respective countries and this is some reason behind this. Bitcoin decentralised nature is the one of the main reason behind this