I caught mtgox doing bad thing and published it couple of minutes before the big fall: https://twitter.com/krtek_net/status/436386804372344832 and https://twitter.com/krtek_net/status/436492419811405824. These 4 trades were made by single SELL LIMIT 1 order which was suppose to create a new low. The order processing went up to bids over or equaling the low, paused and waited for another bid to be placed from another trader and finished with last trade higher then the low. I call it order sorting, I'm aware that this has happened before but it happend to me today for the first time. I've lost goxtools logs of that one, but managed to replicate the same behavior after couple of tries. Trading terminal is connected on Tier 1 network, dedicated hw, no other apps running, 100mbit unmetered. I've checked that my order book is up to date using all available channels and there was no engine lag before and/or during the execution.