Bitcoin can be a bit of a tarbaby when it comes to defeating it. Many conceivable attacks may give rise to consequences that are even more pernicious from the standpoint of a government/central bank. You can be sure this is already being gamed out in the think tanks.
Alternately, a government could make great use of Bitcoin, or a Bitcoin-like system. Remember, onion routing was developed by the U.S. Navy. Gavin has stated (or perhaps, implied) that the CIA had expressed interest in the potential use of Bitcoin as a clandestine payment system. Bitcoin could also serve as a rich source of intelligence through money-mapping techniques, &etc. As such, I would expect that there could be (not a few) Bitcoin related service businesses that act as fronts for intelligence community data collection and operations support.
Aside from that kind of entanglement I suppose that a government could involve itself in attacks on the exchange markets designed to remove liquidity from markets. It would take deep pockets to do this, but even at a billion dollar 'market capitalization' those means are well within reach of a government. Although, given the right kind of intelligence such a trading program could be targeted to affecting the liquidity of an individual trader.
There may be a show at some sort of legal intervention, but I expect that it would be by way of an artful manipulation of the direction of Bitcoin development rather than any genuine effort to abolishing it.
Very good points. To add:
- "The government" presumably means the U.S. government, and its allies. They do not 100% own the world yet, so an outright attempt to discredit/destroy bitcoin may end up just harming their own citizens, while enriching others. Not that they cared..
- The idea of a cruptocurrency cannot be destroyed by rooting up its offspring, the cryptocurrencies. If they want the world to be content without cryptocurrencies, they need to disprove their validity and usefulness. That cannot be done by force. By just wrecking Spinning Jennys, the idea is not destroyed, but rather gains more traction. A 51% attack against a certain crypto would do more harm to the gov than good.
- I am sure the NSA has gathered a formidable database of compromised private keys. This may amount to 25%-75% of all bitcoins existing. We don't even know all the methods they have for snooping us. Even if they wrecked with these all at once, I don't believe it would do more than to infuriate all the honest users against their own gov. Governments typically want to avoid provoking extremism.