Also remember that their buddies the Chinese aren't going to be real keen on them making so much noise. Sure, it's fun for the Chinese to watch them bark at Uncle Sam, but once Japan starts thinking about arming itself with nukes for deterrance, or talks about allowing the USA to base nukes there, they'll tell the little dog to shut up.
Additionally, all we need to do is stall for time. There will be a missle defense system soon enough to protect Japan, and then one that will protect the US. It's no coincidence that Bush is planning on putting the first BMD installation in Alaska (which is the only part of the US they can hit now, and what any NK missle will have to fly over to get here). Once that's done, all of a sudden the North Koreans have nothing to show for all their work. It'd be a bad day in Pyongyang to wake up one morning and realize that all your nukes were made comletely useless overnight.
Ross