Both as a technical concept and as a social phenomena. Quite a lot of people using Bitcoin are not doing so for practical benefits.. they're installing the software and promoting the concept as a sort of protest against the fiat banking system. Oh, and because they hate paypal.. but that's mutual.
http://susansayler.wordpress.com/2011/05/16/bitcoin-p2p-currency-the-most-dangerous-project-weve-ever-seen/
That's a pretty interesting article.. and it demonstrates the power of portraying yourself as persecuted to attract new members.
However, I think they're pretty delusional about the robustness of the system. From the paper that started it all:
If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.
This obviously assumes the attacker is interested in profits that can be extracted from the system. An attacker who is already wealthy, and has a greater interest in undermining the system than extracting profit from it, can trivially overwhelm the network by assembling processing power - especially if the attacker already has a stockpile of processing power.
National governments obviously fall into this category, so if they ever decide to destroy Bitcoin they won't need to issue any bans or even tell anyone.
I'm sure you can think of some other potential attackers who have the capability.