I read an article online that got me thinking about the potential for massive losses the CME could inflict on a trader, without them even knowing it. Read about how the CME recently cancelled many trades here: http://www.thestreet.com/markets/aarontaskfree/10099985.html Here is the important part: "The final-hour fade was apparently precipitated by an erroneous trade of S&P 500 E-mini futures. Late Monday, the Chicago Mercantile Exchange canceled all trades in the September E-Mini S&P contract below 996.00. At 3:08 p.m. EDT, a price drop occurred in E-mini S&P futures that lasted four seconds, and [sent E-mini prices] from 1000 to 990.50," according to Maryellen Theilen, a spokeswoman for the MERC. "The drop was triggered by a series of cascading stop orders during relatively thin market activity." OK, now here is the danger to the trader. Let's say you have a highly leveraged short position late in the day. You also have a buy order to close out the position, which gets taken out when the S&P emini drops 10 points in 4 seconds. You are happy to have been filled, and since its late in the day, you log off for the rest of the day, thinking you do not have a position. BUT WAIT.................... The CME in its infinite wisdom, decides to cancel your trade, for the exact reason detailed in this article. But you don't know that has happened, you have stopped trading for the day. You don't find out the trade was cancelled until your daily statement arrives, sometime in the middle of the night. So you went to bed thinking you had no position, when in fact you had a highly leveraged short position. Now lets say the market gaps up at the open the next day by a huge amount like 5% for some reason like an economic report, geopolitical event, etc. And with your leveraged position, you have just lost 20%, 30%, 40% of your capital, the potential for loss is unlimited. There is so much margin power with the emini's, you could effectively have the potential to lose 100% of your money. And all because the CME cancelled your trade and you didn't know they had cancelled it. Am I missing something here? Because the thought of the CME cancelling trades for ANY reason is a very frightening scenario. And it also opens up the possibility of deliberate illegal market manipulation. If you know in advance the CME will cancel your next trade if you manipulate the market, all kinds of illegal cross-market arbitrade opportunities become a possibility.