As you can argue reading this blog, I'm a WCF lover and in particular I'm really crazy for it's security infrastructure and architecture. Some Microsoft guys have made available a set of great contents ("how tos", "application scenarios", "guidelines", "practices" and "Q&A") indeed to help the community of WCF developers to build secure and interoperable WCF Services. The project is really interesting and I suggest you to take a look at it, before implementing a real WCF solution.