MtGox has never provided a good reason why they were missing so much in various asset classes. They tried to point to "transaction malleability" early on, but p

MtGox has never provided a good reason why they were missing so much in various asset classes. They tried to point to "transaction malleability" early on, but people who have traced such activity say that it can account for only a small fraction of the BTC MtGox claims to be missing. Insider theft or loss of keys seem to be the most plausible theories, though some people think all the money may simply have been gambled away trying to recover losses incurred earlier. Some folks over on Reddit, btw, claim to also have found an additional 300,000 BTC still under MtGox's control. This is perhaps support for the "missing keys" theory, or perhaps simply "gross incompetence".