How much would it cost for a government to undermine Bitcoins? Articles by for example the Economist stating that Bitcoins are being used for drug trading (Silk Road), I believe that the biggest risk to Bitcoins is that a government will pull a stunt similar to Stuxnet. This was also the answer of David Schwartz to a previous question of mine.

Therefore, I believe that we should make a metric, similar to Bus Factor for software projects, which indicates risk of such an event with a single number. I propose that the metric should be called CSU (Cost of Secret Undermining). Later we could calculate the cost of undermining in other ways, like by banning businesses that accept bitcoins and so on, but that will be much harder. 

Therefore, my question is: What is the current lowest CSU (Cost of Secret Undermining). This means, what is the cheapest way for someone (for example a government) to secretly undermine Bitcoins to the extent that Bitcoins are no longer useful as a medium of exchange, for example by utilizing the method suggested by David Schwartz. We should compare the number that we find with the current budget of the US fight against illegal drugs. Of course, the expected impact on the fight against illegal drugs is a deciding factor. Even though it will be very hard, we should try to estimate the development time needed to launch such an attack as this will be a cost the attacker would have to calculate with.

This question is related to this question, but now I would like to know the cost of undermining Bitcoins instead of just launching one single 51% attack.
As I suggested in my Bitcoin master thesis, a 51% attack would cost in a bulk part of about 7 million dollars to execute. The figure will change depending on the technology used, the current difficulty and so forth. This option would make Bitcoin or any other Bitcoin-like currency useless.

However, if the USA goverment was to crack down on Bitcoin as a terrorist activity, it could detain any Bitcoin developer in the country indefinitely, which would probably be cheaper. This option would most likely generate a lot of backlash from the community, and could encourage other programmers to take over the project.