I'm not a conspiracy theorist and, frankly, I'm not sure I believe that what I'm suggesting as a possibility is even possible, but.... I'm beginning to wonder whether the FIFO rules are followed to the "t" when it comes to ES. I don't have any evidence to back this up. I base it only on observation. I'll be happy to go into the details if someone really wants me to, but it's so impressionistic -- and, possibly, paranoid - that I'm not sure it's worth anybody's time. For the record, this is not a "market's out to get me" thread. Also, I would think that the clarity of FIFO -- driven by an algorithm -- would make it hard to throw. But does anyone monitor CME's compliance to its own rules? I'm thinking something along the lines of a given state's measurement standards authority checking on your local gas station to ensure that the gallon it claims to pump is, in fact, a gallon.
skip - It would be nice to know that someone is monitoring the CME to ensure integrity. Perhaps the CFTC and/or NFA do this. That is a valid point. As for the algo being manipulated, we will never know unless something big happens - disgruntled employee, fund(s) that make some allegations, etc. Like you said, there's nothing out there to even think this is happening, so I don't think there's much to discuss, esp among retail traders.
Also check this site and another ET post on a similar topic: http://www.cme.com/trading/get/abt/functionality/lmm.html