No, they'll go after the exchanges and, failing that, users of the currency.

I think any assault on Bitcoin would have a lot more in common with the tactics of the copyright cartels, than this. The decentralized nature of peer-to-peer sharing and Bitcoin is more relevant than the fact that the Liberty Dollar and Bitcoin are both 'currencies' depending on who you talk to. Numerous lawsuits, harsh penalties bordering on unconstitutional (not that it really matters), and selective media exposure of same.