The DPRK kicked out American experts and IAEA inspectors this week, promising to restart its plutonium reactor after launching a missile into the Pacific. This is not a new pattern for the DPRK--for decades, they have played brinksmanship with the rest of the world, gotten concessions in exchange for promises, only to swiftly turn 180 on those promises and start jerking the rest of the world around for more handouts.
I am typically more in favour of negotiation than many of my realist friends, mostly because I think that most concerns by most countries are relatively reasonable. But modern deterrence usually hinges on threats that are low cost to the deterrer, including sanctions or whatnot; negotiations can happen with such deterrence hanging in the background. But deterrence of DPRK will require serious threat. The DPRK won't be swayed by anything sanctions-related, as it controls the media so thoroughly that the country's people will never be angry at the state. Trying to affect public opinion is useless. Kim must actually be scared into acting straight--both carrots and some seriously heavy sticks must be presented.
Some sanctions actually have a shot at disabling the missile and nuclear programs, which is a laudible goal. China may possibly block such attempts, it's unclear--but the audacity of DPRK's continuance of nuclear refining after hard-won treaties against it will even anger the Chinese, who arguably put the most work into the negotiations in 2006 to get the North Koreans to stop refining plutonium in the first place.
The US should be prepared, at this point, to begin considering stacking South Korea with masses of anti-artillery rockets, and bring an aircraft carrier/missile destroyer to bear on North Korea, threatening to simply destroy known refining and production facilities (some of these are underground, unfortunately). The anti-artillery rockets are vital just in case the North Koreans attempt to respond by bombarding Seoul with artillery, or threaten to--Seoul is close enough to the border for the threat to be entirely real. If the US can create a strong upper-hand in negotiations, the DPRK might be more willing to ply. The Chinese will object, but are unlikely to get too involved at this point in their growth phase. The last thing the Chinese want is to give the Americans a stronger impression that the Chinese are bent on propping up rogue states--their relationship with Iran, Sudan, and North Korea as it is gives China a relatively bad impression in the US.
What cannot happen is new rounds of negotiations similar to those in 2006. Such brinksmanship on the part of North Korea is costly and, frankly, dangerous, and it would be irresponsible to encourage such brinksmanship by rewarding it with new negotiations for handouts. The long-term solution, of course, is to try and leak free information into the DPRK to push for domestic regime change. The brainwashing by the DPRK government is so thorough that any external attempts to depose the regime will be met by massive backlash (and, of course, refugees), so any attempts to oust/depose/bankrupt the DPRK will probably not go over so well (both South Korea and China virulently oppose bankrupting the DPRK, as they would have to deal with millions of starving refugees all at once--not a great plan).
So, Mr. Obama--time to get tough. Let's see if you can do it.
EDIT: I've since been informed that, should a conflict with DPRK arise in which the DPRK was sufficiently more prepared than the US/ROK, ~0.5 Million shells would land in Seoul during the first hour of the conflict--there aren't enough Patriot or Aegis batteries in existence to deal with that. Surprise operations, including airpower, commandos, etc, would be required to disrupt DPRK operations enough that those artillery batteries could not be brought to bear until enough US planes were in their air to blot out the sun.