> The government could probably mine 30000 coins in thirty minutes on spare CPU power on some defense computer system.
No they can't. The combined hashing power of the bitcoin network is 1.15 million Petaflops. The top 500 supercomputers in the world have a combined power of 250 Petaflops ( http://s.top500.org/static/lis... ). Even if there are hidden NSA machines or whatever, they don't account for that big a discrepancy.
The reason the bitcoin network is so much faster is they use custom chips that do nothing but the SHA1 hash calculations used in mining. It's directly wired into the transistors, they can't be used for other math. But you can pack tens of thousands of copies of that algorithm on one chip, and mining rigs have boards with ~36 chips each, and multiple boards.
Also, the network difficulty adjusts every 50,400 coins (2016 blocks @ 25 coins per block), so if someone *could* mine that fast, the difficulty adjustment would bring it back to the normal rate (300 coins per hour) rather quickly. Lastly, that high a mining rate would be considered a "51% attack" on the network, and the rest of the network would rapidly reject the blocks and fork the history.