A federated identity can be used to provide a single sign on to multiple applications, both in the enterprise and in the cloud. Microsoft has adopted a "claims-based architecture" in its approach to managing the identities of users in its Azure cloud.
At its Professional Developers Conference in L.A. recently, it announced a Microsoft Identity Platform that invokes the architecture to establish a federated identity for users. A federated identity can be used to provide a single sign on to multiple applications, both in the enterprise and in the cloud.
A federated identity of some type is going to be necessity if there is any prospect of hybrid cloud computing coming into vogue. IT departments that ship part of their workload off to the public cloud will need to be able to allow end users of applications to follow them into the cloud and use them there as well.
Read full story… Windows Identity Foundation overview (on-demand session from PDC09)