A government attack is a significant risk. Think about China: they have the resources to pull off the heinous deed.
I should apply XKCD's famous "$5 wretch" argument here: if an authoritarian government wants to screw you, there are much easier ways to do it than a 51% attack, otherwise if they want to play, they would be very careful to not tip the balance.
Like what?
Shutdown ASICMiner and Avalon, arrest everyone and scare the daylight out of all the remaining Chinese miners.
That's far from the destruction of Bitcoin. They can do what they want in China, but not the rest of the world.
No, per the status quo it would have the same effect: right now there is no viable ASIC producer out of China(BFL honestly is not there yet), if there will be at least one in the future, whatever China will do doesn't matter, people can just switch to the out of China producers. If there will not, then the "$5 wretch" attack still works.
Even if there were no more ASICs produced, the current nodes would maintain the network.
You didn't get me: the "$5 wretch" attack applies because had the CCP wanted to 51% attack the network, the easiest way to do it would be to arrest the ASICMiner/Avalon people for things like tax evasion, and confiscate all their blueprints, drawings, VHDL programs, manufacturing equipments so that they can easily replicate their own ASICs. Why buying/developing your own when you can get them for much cheaper?
Besides, given how competent friedcat has been demonstrated to be, it's most possible that he has already correctly assessed the risk.
OK. That's another whey they could pull off a 51% attack.
It would be so visible that it makes no sense to pull it off at all.
Why would they care about visibility? Bitcoin's not a national currency.
If they don't care about publicity, I believe they would do it my way, as long as everyone is safe and sound, no need to worry. If they do care, then they would not pull off a 51%. Of course there are all under the condition that China is not interested in Bitcoin itself.
Also, it needs to be pointed out that Bitcoin is great because it doesn't care about your political ideology, cultural background, social status and whatsoever, everyone can benefit from it other than possibly the staunchest banking system supporters, it's best not to make too big a fuss out of this if we don't have hard evidence.
How can there be hard evidence, if it hasn't happened yet? And you've just given an example of how it can happen.
Of course, Bitcoin is revolutionary. But ignoring an issue doesn't make it go away.