Mt Gox, once the largest Bitcoin exchange in the world, is operated from an unmarked Tokyo office block that offers no indication of its major, controversial influence on the digital currencys health. Mt. Gox: Where is our Money, reads one sign. Mt. Gox: Are you solvent? reads another. Bitcoin trader Kolin Burges started the protest last week, flying from London to seek answers about Mt. Goxs ongoing moratorium on withdrawals.