I wouldn't go so far as to say that it is a scam, but I believe it is at the very least deceptive practice and I would go so far as to say that it is a breech of contract.  The text on the site defined a trading session is 24 hours, with a maximum trading range of 10%. Fireball, could you provide the original text that was on the site before you updated so that it can be considered? 

I had contracts of BUJ3 with enough money in reserve to handle 10% movement, and had my finger on the button to add additional funds if the clearing proved to move the price down to a range that might put some of my contracts in jeopardy.  The clearing actually moved the price range center from 103 to 106, so I did not add additional funds. The manual clearing I believe moved the price range center to 95, causing a loss of a very large portion of my positions as the price went down to 86. I've since closed all of my positions at a great loss to myself as I've lost all confidence that this site will perform as it says it will without making things up as they go.

I feel that this manual clearing should not have happened according to the definitions laid out on the site at the time. I feel that the exchange did this as a CYA disregarding the fact this is not a provision set forth and agreed upon with its customers. Some sort of compensation is due.