[prutschman]

My understanding is that blockchains are designed to ensure that it would be economically irrational to attempt to expend resources competing with the blockchain, creating create a stable equilibrium in which rational participants cooperate.

It might not be worth a scammer's money to buy enough computing power to double-spend, but that doesn't mean a government mightn't find it worthwhile to spend money to tamper with or destroy something it perceives as a threat.

[natrius]

Blockchains can be tampered with, but they're tamper-evident. Sure, a government can 51% attack Bitcoin and lower its value. The value of Bitcoin doesn't matter. What matters is the ability to reach consensus on a sequence of events. Such attacks only make that harder temporarily.