[gritzko]

A real bad thing here is the asymmetry. To prevent 51%, the network has to burn enormous amounts of energy 24x7 forever while the attacker only needs his energy for the duration of the attack.

[lukifer]

Counterpoint: physical security largely works this way too.

[gritzko]

Well, things work much better in crypto (not proof-of-work, but the "real" one).