I've been thinking due to the volume of trade on bitcoinbuilder, and the efficiency and timeliness of the exchange, that it could be possible that bitcoinbuilder was mtgox coordinated effort to facilitate the selling of goxbtc (which mtgox can fabricate) for real btc in order to raise funds.
Gox, or a company planning to takeover Gox, can right now buy 8 GoxBTC IOUs for 1 real BTC at BitcoinBuilder. This would be a legal way to give depositors a voluntary "haircut" outside of bankruptcy. Eyeballing the bitcoinity chart, it looks like they've done about 80,000 GoxBTC in trades. A lot of this was swing trading, but perhaps 20,000 GoxBTC have been bought for an average price of 0.25, or 5,000 BTC.
Of course we can't know, but if this was a coordinate effort to buy up the IOUs for cheap, then this action could have reduced Gox's BTC liabilities by about 15,000 BTC.
If the 750,000 BTC loss is FUD, this might make sense...
That's a good way to look at it thanks! Would it not be possible for Mtgox to credit an internal address with 1000 GoxBTC / IOU's, deposit them on BitcoinBuilder and buy up real btc?