Bitcoin has been around the borders of financial markets for less than a decade, but is slowly gaining importance as an alternative asset class.
Can the government of any major country step in and do the unlikely?
Yes, I think they can, They already banned bitcoin in Thailand,China,India, and Bolivia.
Other countries like Russia,Germany even Taiwan developed a policy and regulates the used of bitcoin. Its possible that their government considered alternate currency to be unstable and uncontrolled they have difficulties on how to impose regular taxes on it.
They might also consider the possiblility of Cyber theft that could cause bankruptcy and also the chance of getting into some fraud schemes.