I work for a finance related technology provider and as a consequence get to see the technology practices of many brokers and other market makers. Often times t

I work for a finance related technology provider and as a consequence get to see the technology practices of many brokers and other market makers. Often times their security is just as bad. The key difference is that trade settlement (a.k.a clearing) is a separate process (usually also separate company from exchange). This adds a layer of security because compromising the exchange doesn't always get you access to the clearing details. Clearing details are usually things like "Depoist X million dollars in bank account A, I will deposit x million euros in your bank account B." With Bitcoin quoting, trading, and clearing are all rolled into one.