It's definitely uncharted territory since anything similar seizure or FinCEN wise has been e-currencies versus a new currency with its own set value.
It's not really uncharted territory. There are countless examples of countries (the more despotic the more likely) outlawing or restricting currencies and precious metal. In fact we see this to a large degree with bitcoin today. I imagine the usage, and therefore value, would be a bit higher if you didn't have to worry about having your bank account shut, an audit generated, or $ in your trading platform seized due to govt (banking industry) attempts to damage bitcoin.
However as someone mentioned, bitcoin is global. When a govt tries to outlaw a certain currency or metal, generally this only has a very limited effect on the value you can obtain when selling within that country on the black (free) market. Plus bitcoin is so much easier to transfer out or into a despotic country. I'm guessing that outlawing in the US would create an almost insignificant value differential compared to the world market.
There is a second half of the equation, since currency has ultimate value because of the user pool and the investment pool. At the moment I'm guessing the investment pool in bitcoin accounts for far more value than the user pool. I don't know that "making it illegal" would currently stop too many US investors who wanted to buy, however it would certainly cripple the legal segment of our emerging user pool. If the entire US commercial bitcoin market were shut down, that might remove 1/3 of the potential worldwide user pool for the next decade. However I still don't think it would do too much damage because most of the value would still be derived from investors, overseas users, and the illegal user pool in the US. All it would really do is wake up and piss off a lot of smart people.
The only thing that worries me is if the govt can crash bitcoin thru some software attack, because I don't know enough to guess at their likelihood of success that way.
