This is not new. There were and are many currencies independent of any government (Disney, Linden dollar, local currencies) but Bitcoin is the first project of currency fully decentralized, independent of any central authority. This is something really novel.
Usually, the cost of destroying something is much cheaper than creating it. That's why terrorism can work. The cost of attacking is not that large compared to fear, destruction and cost of guarding. 9/11 proved it very well.
In case of Bitcoins, obtaining 50% of the network compute speed required for completely disrupting the Bitcoin network grows with Bitcoin size. When Bitcoin network compute speed crossed the fastest supercomputer Tianhe-1A, it is no longer that easy. Destroying Bitcoin network is roughly as costly as the Bitcoin economy size and if it grows, it will become even more costly. This is not asymmetric as in case of terrorism. It is still possible for national governments but it's no longer a matter switching on a small cluster.
Usually, the cost of destroying something is much cheaper than creating it. That's why terrorism can work. The cost of attacking is not that large compared to fear, destruction and cost of guarding. 9/11 proved it very well. In case of Bitcoins, obtaining 50% of the network compute speed required for completely disrupting the Bitcoin network grows with Bitcoin size. When Bitcoin network compute speed crossed the fastest supercomputer Tianhe-1A, it is no longer that easy. Destroying Bitcoin economy is roughly as costly as the Bitcoin economy size and if it grows, it will become even more costly.
Actually, he was was in the second car of a two-car tram. He switched after the first car passed forcing the second car to go the other way.
One man's constant is another man's variable. -- A.J. Perlis