Thank you for being logical. To put it another way: If every trader's market data is the same, for a given system Input (market data) .... System (processing of data) .... Output ("buy", "sell", etc.), use by more traders will lead to more traders attempting to execute the same trade at the same time. That's more competition.
No, What I am saying is, if Input(data) isequalto price will evaluate to true less and less as more traders know about it until it _never_ evaluates to true because "price" will be anticipated by more and more traders as it approaches the value of Input(data). This is clearly an idealized case, as even situations that are "risk free" occur all the time even though lots of people know about it, e.g., Index Arbitrage. But the more players that have entered into that game, the less the guy that thought of it makes, until all you are left with are scraps. nitro
There's no inconsistency there. Mine describes the conditions (more competition). Yours describes the result (uselessness of the system).
The more people exposed to an arb, the more likely someone will be willing to do it larger and for less edge. Then someone comes along and pushes that clown out of the way. In the end , lots of money is made by the block box boys and nothing by civilians.