To date, the vast majority of real-world federation roll-outs have been internal or enterprise type deployments. Things like an enterprise authenticating its users out to an outsourced provider (such as a Fidelity 401K, or AOL's Radio Service). Yes there are many exceptions to this general statement (you can see many of them on Liberty's Adoption Page ), but that is the general view of the industry and I certainly don't knowingly use federation in any cross-provider operations. The time has come