Look at North Korea's history of bold statements and threats, it has been going on forever yet they are still on their side of the DMZ as they have been for over 60 years. Kim is NOT insane and he does not want to die and kill his entire country. They like to threaten because there is no real downside to it for them and it gets them attention. Obama had it right, ignore them when you can  and like a child having a tantrum they will see it is getting them nowhere and eventually they will stop and try a new tactic.