Do you think it's clear to Kim & co. just how many South Korean soldiers, airmen and sailors he can kill without triggering the war that no one wants? He got 46 this time; had the ship's entire crew of 104 been killed, would the reaction from Seoul and its friends be any different? (Hint: No.)
So what's the answer? If not 46 or 104, is it 460? Or 4,600 perhaps? What's the red line that Kim Jong Il cannot cross without eliciting something more than yet another round of economic sanctions from the U.N. and an inter-Korean trade embargo that doesn't really put an embargo on inter-Korean trade? I bet he doesn't have a clue. And that's what's scary.
I suspect that, if past performance is any indication, the DPRK leadership knows full well that provocations, even those that result in significant numbers of deaths--1968 Blue House raid, Pueblo incident, ax murders, Rangoon bombing, bombing of KAL 858, numerous clashes along the NLL, shooting of a tourist at Geumgang etc. etc.--will not result in a significant military escalation on the part of the ROK (or the U.S., Japan etc.). The real question is less what the DPRK will do and more whether the ROK has finally had enough and will escalate.