Swoop[TR] wrote about FX brokers: "They don't really care that you make money or not, they're just matching bids and asks."
I disagree mightily, based on my first-hand experience trading a large account with Saxo Bank, which is one of the so-called spot FX "brokers." First, Saxo is not a broker, but a dealer.
Saxo is the counterparty, trading against the customer for its own account. It doesn't broker someone else's position or contract to you. It books the bet itself, unless, as was true of my account with it, it does not like the price of the trade and refuses to honor the order. That happened 4 times in one week in the account I traded, each time after the price of my order (a limit order) breached and then exceeded the price streamed to the Saxo platform and shown on the platform chart. Received excuses like "quote misfeeds."
No doubt, even as it refused my limit orders, Saxo stopped out other customers betting the opposite direction of my trades. I say that because, first, the prices charted in my positions were never corrected for the so-called "quote misfeeds," and second, in other trades, Saxo always filled my stops instantly, no excuses or problems. But with the stops, of course, Saxo made money as the counterparty. "Quote misfeeds," etc., only occured when my orders would have caused Saxo to lose.