It's more like taking a peek at the other players' cards, when only you have the ability to do that. Yes and no. To continue the analogy, if your counterparty

It's more like taking a peek at the other players' cards, when only you have the ability to do that. Yes and no. To continue the analogy, if your counterparty checks his cards every few minutes, while you are sitting at the table and monitoring continuously, is that your fault that your decision making strategy has a much tighter feedback loop than his? In a lot of ways, the HFT practitioners and the portfolio managers (or other active, but infrequent, trader) are playing complementary, but very different games. The portfolio manager wants to move large blocks of stock, and pays for liquidity. The market maker facilitates the motion of large blocks of stock, and charges a premium for assuming the risk of adverse, short-term market movements.