Bitcoin might be awesome. I don't think it really meets the definition of money, but it may still provide a way for market order to emerge globally, in direct competition to governments. Bitcoin, as a network, may be far more important than whether or not Walmart ever accepts them as currency.
But, in order for Bitcoin to prove out it's awesomeness, it must be stepped on by USG, survive, and thrive. Technically it can. It is peer-to-peer, so it will be a lot harder than, say, shutting down Facebook. If the government wants to shut down Facebook, well they've got a particular place to target. If they want to do that for Bitcoin, well, they've got to go many places. It may still be doable, but it is far more problematic.
So, a really heavy handed attempt to end Bitcoin could actually lead to its widespread adoption. There are rumors of ddos attacks on particular Bitcoin related businesses, which leads me to wonder if some in government understand this and have chosen clandestine responses rather than overt ones precisely for this reason.