Some government banned Bitcoin because it could affect individual security and world economy. In terms of security, a person can buy a drugs or illegal stuff without giving his/her personal information using Bitcoin. So, it easily for a bad guys like terrorist to transact across the world.Government afraid that Crypto Currency like Bitcoin will replace the fiat money or Central Bank anytime soon. People can earn money by investing, buying, selling, and build their own business without paying right taxes. In that case, government fund that support government workers and maintenance of public road and places will be affected.