It's pretty transparent that these hackers are North Korean. Fuck North Korea.
Really? What would North Korea have to gain by doing this? They already have less than one friend on the global stage (ie, only partial support from China). If they go around encouraging cyber warfare like this they are only inviting more pain back towards themselves.
Even more so this is likely beyond the technical capabilties of North Korea. Some people have suggested that this hack took upwards of 100TB of data. First of all, it is unlikely that North Korea has the ability to move that much data through their connection to the internet in the amount of time that transpired. Second, even if all the "best" hackers from North Korea did their best job to steal this data and place it elsewhere, it would have been pretty easy to figure that out as well.
So really, scratch North Korea off the list.
Some people have suggested that the hackers are "sympathetic to North Korea". To this I say bullshit as well. If someone wanted to make North Korea look like victims, launching a cyber attack is not a good way to do that. And how would a cyber attack on Sony make North Korea look strong or capable?
I would say the most likely case is we have some hackers who really despised Sony and found a way in. They then laid this "North Korea" cause as a red herring.