You're forgetting that at any point, any government can prohibit using bitcoin, as they did previously with gold, and may prohibit using these scripts. What's left?
Sure, you may not be able to purchase things locally with it, but it's just a computer program and information, you can hardly prohibit with any force. Look at tor.
jimktrains2 if the gov decides that bitcoin should be made illegal, most people won't bother with it. And if you can't use it locally what value does it have at that point? Gold you can at least bury in your backyard and hope that if not you, then your grandchildren will get something out of it.
