I don't see how having a black box system would make you anonymous. Black box or not, you would still need to have an account with your liquidity providers and they'll always know who you are. The correct term for truly anonymous trading is "dark pool", not "black box".
ok, then I stand corrected, but I'd hardley call displaying the price rounded to the nearest .5 pip getting screwed, especially when it is not uncommon to get filled at the better price. But then again, I'm not trading 20m.
there is a reason why most consistently profitable speculators use spot market and phone. although never trading big size, got a fair share of screws. Enough to decide to move away from shortterm trading. Some math: there is around100k contracts net short position in eur. This is 10B. Moving market 3% gives profit potential of 300M. Most of it will go to the guy running the show. There is maybe 20M left for others to pick up. Not that much really. Intraday, divide these numbers by 100.
yes, that may be true, but how does that affect a small trader like me who may at any moment buy or sell at the market a small position? The Original Posters question was when in spot forex especially with an ECN like IB does size become an issue? He already states he can move 2 to 4m with no problem, but he is looking ahead to 20 to 60 m.