I should edit my comment to non violent regime change in North Korea. The fact is that its only China that keeps Kim Jong IL in power, and without Chinese support, the North Korean government would collapse like a house of cards.
As it is this incident comes at the correct moment in history, Kim Jong IL is dying, and if left alone, the North Korea government would be led by Kim's unknown 20 something year old son, or fall to a military takeover. The latter could not succeed without Chinese complicity and would solve little, letting sonny boy to follow in his daddy's footsteps would also solve nothing for China, and the other option of China simply annexing North Korea would not set well with the rest of the world.
For China, the best option might be for Sonny boy to take over, have China advocate a
a Korean unification under South Korea, have China and the West bribe South Korea to undertake a Marshall type plan to modernize North Korea, and then it becomes a win win win for everyone. Sonny boy gets some political plum post with all the ribbons he can cut, and China becomes an international good guy while gaining economic ties and trade relations with all its neighbors while losing a loose Canon on its borders.
Or alternately, China might work with Sonny boy, demand that North Korea get a civilian international trade based economy, and China still wins and everyone else wins also.
The only lose lose situation we now have is the current North Korean failed State that not only can't feed its own people, it also benefits none of its neighbors.