We are engaged in a cyber cold-war. The primary adversaries are the US, China, and Russia. China has directed attacks at the US, Russia has targeted former republics, and the US striking at Iran. With respect to the great powers, Mutual Assured Destruction (MAD) is in everyone's mind. The 5th wave nations are all incredibly vulnerable to cyber-attack and as Anonymous and others have shown, no one has even a modestly effective defense.
IMHO, the MAD risk of cyber will keep the major powers in-line, just like it has done with nuclear. However, the cyber-weapon genie is 100 times more difficult to keep in the bottle. We are fast approaching an era where a cult or perhaps even a lone gunman could use Stuxnet or perhaps now Flame as the blue print for a devastating attack on critical infrastructure.
Lastly, these weapons often effect more than their target. Collateral damage, friendly-fire, and blowback are more likely with a cyber-weapon due to the nature of cyberspace and the difficulty of distinguishing friendly systems and networks from those of the adversary.