It really depends. Some governments do not want multiple currencies that compete with the currency it controls. It threatens the governments financial control. On the other hand, some countries could care less, especially the ones that are not tecnologically advanced.
That was the case with the Venezuelan government when they decided to crack down on those that were mining bitcoins in the country, even with all their efforts, people are still mining bitcoins, nothing can really bring down completely even in the case where they ban it and the value plummets, it sure to rise up again.