I think there is plenty of blame to go around:
First, to the despicable Pyongyang regime, whose proclivity for brinksmanship lies at the core of this.
Second, to the leaders of China, who have conducted an decade-long effort aimed at diplomacy with the North Koreans instead of sanctions. Clearly, they were the country with the most leverage, and they frittered it away.
Third - to the South Korean government, who also resisted sanctions on their bellicose northern neighbor.
ooh - -and lest we forget - the Madelaine Albright kumbaya moment - - aided and abetteed by that master of foreign-policy - Jimmy Carter.
I suppose, however, that those blinded by Bush-hate will try to rewrite history with a simplisitic comdemnation.
If you're aiming that at me, at least you didn't call my feelings toward the man "irrational."
When a country repeatedly bullies others, includes threats of regime change as part of its interaction with them, generally refuses to have any dealings with ones it doesn't like, and invades one with no provocation, then one shouldn't be surprised if some of those other countries (Iran and NK) try to find weapons which might give that country pause before it did something in an attempt to change their regimes.
North Korea is not a sensible country in much of anything, but in this case I think it's perfectly rational from its point of view. Iraq = no nukes; result = invasion. Iran = nuclear threat; result = no invasion.
If I were the leader of North Korea, I'd learn from those two observations.