I can agree on full disclosure for big bureaucratic organisations that ignore you when you report a bug.

But honestly, in this case, for a small company like MtGox. I think that makes you a dick. MagicalTux is really taking all problems seriously, and has been working almost 24 hours per day last week to resolve issues while being bombarded with crap from all sides.

You could have given him a chance by just reporting it to his personal mail and bug tracker. What would you prefer if you had built a site yourself?