Yes, however, what if governments ban it? If copamnies are forbidden to sale with Bitcoin, very few things will be able to be bought with it (only illegal). Don't you think this can drop price? You see what is going on in China already...
Well movie/music file sharing is illegal and look how successful they've been at stopping that. I don't see how they could totally ban bitcoin without introducing a load of new laws and legislation which in itself would create another huge global privacy debate. Bitcoin has been adopted by the people for the people. That is a scary thought for governments and the puppet masters behind the scenes.
They would probably use laws already in existence. Here's a good article:
http://www.wired.com/wiredenterprise/2014/01/stampact/ The legality all depends on the pressure from the banks and from people using it to prevent the payment of taxes. If those problems rise, we would see a push towards a ban.
Basically if the banks get scared, which they inevitably will, that's when we will see problems imo. And the problem with Western governments is when people with money aren't happy (we have conservatives in power atm, help us!) then they pressure the governments to change the law. If they make cryptocurrencies illegal, how will they possibly enforce it though? The Pirate Bay is "banned" and that doesn't stop anyone using it.
If they push it underground, i reckon the price will massively increase, just as the price of any illegal drugs is so high.