What is the value of WIF to developers?
With Windows Identity Foundation, developers have a single programming model for handling identity in an application, regardless if that application is hosted on-premises or in Windows Azure. Productivity is enhanced since you only need to learn one model and one set of tools, and those skills translate quickly if you change hosting environment. Since the model is the same regardless of where the application is hosted, using Windows Identity Foundation will make it easier to move an application (from an identity perspective) from on-premises to Windows Azure, and vice versa.