The America ' fuck yeah' is strong in this thread. People calling Sony cowards and disgusting for caving to ' terrorists'. And how they should grow a spine and just release the movie. Can all the brouhaha, moral outrage and macho rhetoric about how North Korea can't touch the almighty US of A stop for a moment? Sony is recovering from a massive cyber attack which literally crippled the company and severely damaged their public image. The hacking being succesful is also not Sony's fault if the hack was perpetrated by North Korea. Any system can be hacked, especially if the hackers have the power and backing of a country behind them. Any normal corporate security system would eventually fall to such an attack. So while dealing with all of this and trying to recover they are being threatened with even more trouble which could very well sink the entire company considering how vulnerable it is right now, so on that account it also makes sense for them to go into full damage control mode and removing said offending piece to get some breathing room.
Now on the subject of the attacks. If North Korea is behind all of this, they do have the capabilities to strike at targets in the USA and in Japan. They might not be a global superpower but they do have a well trained military that is also zealously loyal to their leader who they perceive as divine and would do anything for. So it's not inconceivable for them to send some of those highly trained people to the US and/or Japan under a false passport via different asian countries to then plan out and execute attacks. This isn't just some random terrorist group in the Middle East with only a few hundred or thousand backers who have poor training and have trouble leaving the area because incoming flights from the Middle East are closely monitored when they arrive in the US. This is not so much the case from flights coming out of Asia which is generally a trouble free zone, with the exception of Birma/Myanmar. So they could probably get into the country with little trouble and have the training and willingness to carry out these attacks. Is this a slim possibility? Sure, but it's not so unlikely as to not be considered at all.
And to the people crying: 'Well then the USA will just bring down North Korea with it's superior might!.' I say that North Korea is backed by China which would complicate matters and North Korea has weapons of mass destruction which include nukes. They can't hit the US or probably even Japan. But they sure as hell can blow up their own country + half of South Korea in a last act of zealous desperation. Seeing how they are all completely bonkers one can't know how they'd react but the potential for catastrophic escalation is definitely there. So I'd say that the US would probably not take that chance. Over a few movie theatres being blown up.
And as others have said. Even if this is not done by North Korea but some random nut job shoots up a theater while this movie is running with all the publicity and controversy going around, Sony will get blamed and the company will be burned to the ground through the moral and financial backlash. The risks simply outweigh the gains. And in the capitalistic society we and especially America holds so dear that is ultimately what counts for corporations.