If there is an US gov investigation which is forcing Mark to cooperate they could issue a gag order, that would explain the silence.
That would be extremely interesting, seeing that Mark is a French citizen living in Japan.
Silk Road users could very well use gox to withdraw cash or buy btc on the early years.
This alone is an excuse for an intervention given that Japan is a very cooperative jurisdiction, not farfetched to imagine a cooperation between Karpeles and the US gov given that he has seized assets on US.