It's not their fault your account got hacked.
No. In this case the Mt Gox is also equally responsible for the hack. They were the ones who accepted fake documents from the hacker and passed them.
this is what i want to say
hacker not just hack my mtgox account only.
my btce account was been hacked too.
and there is 4400USD been stolen
but that is a common case,someone lost password and stolen.
the main liability is not on btce
in this case,mtgox ignore the warning and pass the false documents
that is the main liability.