Does anyone here remember egold? An ecurrency that was shut down by the US Government. What's to say they won't do the same ehre?
If you haven't read the following, please do:
Remember though, bitcoin is just data. The assumption is that if there were government action, the first moves would be directed towards the exchanges. Without being able to easily exchange bitcoins for fiat, and vice-versa, at this stage would have a significant impact on the market value -- which affects everyone, not just the country(ies) that the government took actions.