[Frogolocalypse]

In practical terms a 51% attack is not good, but actually has a fairly straight-forward solution to solve. Change the PoW. A 51% attack can't steal your coins, only restrict your spending them for the length of time they are conducting the attack. So the issue isn't that you have 51% attack possibility, but that people think you do, and furthermore think you're going to abuse it. If a government attacked it, they'd simply hard-fork away from the mining algorithm, and millions of dollars of hardware investment gets flushed down the toilet.