Why is the situation on the Korean peninsula considered the most dangerous in the world?
There are more then one dangerous areas in the world today. Taking into consideration the fact the question is 9 years old, the fact is that the Korean peninsula remains a world "hot spot".North Korea is a communist nation with a family hold on the communist party there. The individual who inherited the top government position is a young man who has taken the place of his father. North Korea has a dangerous missile capability and is frequently at odds with the US, South Koreas and Japan.
It spends the largest percentage of its GNP on the military than any other government, despite the fact that there are "food" problems in N. Korea. It has in recent years demonstrated that it has the ability to launch long range missiles.
The US, even under the current Administration, keeps about 10,000 marines in an area that separates South & North Korea. Lately it has been the suspect of high profile cyber crimes. For all of the reasons mentioned, the Korean peninsula remains a dangerous place.