So some people have more information than others. Just like everywhere else in the economy. Boo-hoo.
I think the argument is that the mega-firms are using these programs not for fast transactions but to post many, very small transactions to determine the top price a potential buyer is willing to pay, canceling each transaction until the top price is reached and then buying the max at the high price.
It would be like select people on Ebay knowing what the top price everyone is willing to bid and increasing the bids behind the scenes so that the item sells at the highest price of the top bidder.