I don't know about stocks, but I called a couple of futures firms, and they told me that most have a company policy that brokers can't trade their own futures accounts. I think this is because the CFTC / NFA require that if a broker trades his own account, then someone from that company needs to monitor the trading to make sure that the broker isn't "front-running" the orders of his clients, which is obviously illegal. My guess is that most companies don't want the hassle of having to pay somebody to monitor their brokers.