That's what they do. It's the design on the whole algorithm. They need money to make that market move. And they will take it from the uninformed, the greedy the spooked, and the downright gamblers..
It's the brokers you should be really scared off. If brokers trade against their clients, they can fiddle with spreads just to even clean out pros that worked hard on theirs planning..
Brokers are supposed to be the middle man between traders and liquidity providers.. all trades should be executed directly to the interbanking system and the only way they benefit is through handling fees. Not trade against newbies that they know they will lose for sure within 90 days..