Because an ECN passes all its trades along to the institutions it receives pricing from there is little chance of price manipulation taking place. It is also possible to get excellent spreads from the ECN broker during periods of great liquidity. In some cases, you could get zero spreads on the most liquid pairs like the EUR/USD, USD/JPY, or GBP/USD. Even when there is a spread it is often quite low since the ECN broker gets its prices from a number of sources. Scalpers can do better with an ECN broker too because their pricing tends to be more volatile.