Hi Danny,

Great question. When you trade in round lot numbers (read: human-ish), like 10, 20, 25...100...150, and so forth you indicate to algorithms that you are a human trader; that you will trade slowly; and that you are most likely uninformed as to the way their algos will manipulate your price.

As an example, once the algorithms are in place they may quote dangle your brokerage's trader. This is kind of like a situation in which there is one very desirable doe among some stags. When the doe does something flirtatious she pays attention to which stag emerges from the crowd to follow her. She then walks several paces away and sees if he follows. If he follows then she goes even further away. Each time making the stag's interest more obvious. If the doe were a HFT then the price you pay can end up being much higher in order to consummate your trade.

A part of why I wrote the post is that most brokers do engage in the practice you describe. They will have to adapt. I wouldn't be surprised that once the HFT issue is better understood by the popular press and the "little guys" that brokerages will begin competing for business based on their savvy execution of trades.

Good luck out there,

Jason