You're absolutely right when you say that the brokerage could make money by front-running you. But so do the exchanges the broker is operating on. After all, we

You're absolutely right when you say that the brokerage could make money by front-running you. But so do the exchanges the broker is operating on. After all, we don't even know who operates btc-e, Bitstamp is slightly more transparent, Coinbase a bit more. The whole industry is completely unregulated so everyone could cheat you until it matures and some rules are set.