Well, how virtual money might work if the world run in a worldwide bankrupt? Without real money i can't imagine companies still running power, computers, networks and without them how the virtual money might work? Outside such scenario governement are probably not liking such virtual money because it's propably easy to hide revenues from tax or to use it for controversial purpose... i suspect they might control or ban such virtual money in the futur because they might lose some control on people if they don't do it... ? i recently heard about qiwi money that is banned mostly everywhere but russia...
So what if the government bans bitcoins? It isn't like they can actually enforce it.