What we all have to eventually realize is that if Bitcoin spreads to a large enough audience, government is going to catch on and shut it down.
How?
Well, other p2p networks have been successfully shut down in the past by governments or agents given power by governments.
Measures could include:
* sabotage (eg. by setting up thousands of dihonest nodes)
* negative publicity (eg. making BC responsible for "supporting terrorists")
* shutting down/ blocking websites that offer the software for download
* imprisonment and legal threats to anyone who contributes to the software's development (eg. by using the pretext of "facilitating kiddie pron trading")
* legal action against individual users of the software
* Introduction of draconian laws and stiff punishments that put off a large proportion of potential users.