Since WizSec's last report was published, the theory Mt. Gox's bitcoins were lost over a period of years beginning as early has 2011 has gained some traction. If so, it suggests your insider must have been active over a long period of time. From what I understand, there were only ever 30 people including contractors working there. If the insider was not Mark, then s/he should be easy to indentify. Who was this sneak?
My thoughts would go to an unhappy employee. People can do various things when they're unhappy and at some point the business in MtGox was booming. Too many transactions, too many responsibilities, probably the worst part was an autistic MK towards his anxious people. Frankly, I cannot say for sure. It's only a hypothesis that is yet to be proved right or wrong.
I would probably agree. It is too obvious for MK to have done it all intentionally himself because all fingers would just point to him, and given that he apparently kept company & customer money together in the same account almost anything could happen to customer funds (fiat) before it was noticed.
At the same time, can we be surprised something like this happened to a man who (allegedly) slept in a $48,000 canopied bed?