I happened to be visiting a TIBCO CEP client in the banking industry last week when the UBS “trading fraud” story gained steam. Some of the smarter investment banks are using technologies like CEP to get a handle on risk management, which has been, and will always be, a significant area of interest for banks and their regulators. As far as CEP technologies go, risk management is usually concerned with trade-state management make rule-based approaches more interesting than the trade-stream approach typically used in automated trading systems (and hence the useage of TIBCO BusinessEvents rules technology in this space over the usual ESP stream processing engines).
Risk and governance are of course often seen as aspects of the problem: situation awareness and track and trace of trading events. I hear that at least one TIBCO customer for example is using CEP for Dodd-Frank reporting (also considered a TIBCO Hawk monitoring rule engine as well as TIBCO BusinessEvents CEP use case).