Is there any explanation for how Akihiko Kayaba managed to trap everyone in SAO?
I've read the Light Novels and it doesn't really cover any more than the anime on how he managed it. And in all honesty, its entirely possible that he was able to slip all that coding in. My father is a programmer so I have a rough idea on how much code goes into a lot of projects and there are actually very few times that people get to view the code as a whole, with each person or group working a small part and then sending it in to add to the bigger project. With this knowledge in hand, being able to work that much code in wouldn't be too far fetched even if Kayaba wasn't top dog, but since he is it is very conceivable that it could happen.