Private, 1st Class
They can but do they? I haven't heard any stiry like this. And I know for sure in my own experience that there are no problem using EA.
Have you met people or heard about a such kind of situation with brokers?
Brokers are supported by banks which provide their liquidity. As far as that liquidity is not serious enough nothing will happen. But believe me that they will cut your wing as soon as they see many accounts are winning money at the same time on the same trades.