Business employment verification (name & login)
My company publishes (securely and privately) a server (such as OpenID) with employee names. When I register for Virtual World C, I point to that server to authenticate my identity to create the account. Interoperability standards enable Virtual World C to identify and obtain a token from that server that validates the employee. When the employee leaves, they're removed from the database and their account is no longer accessible.
This lets the company manage my account status through its existing employee management tools - when I leave the company my name won't appear on the OpenID server and any accounts established with that identity will no longer be available. Rather than a company having to manage employee lists in multiple virtual worlds, this lets them manage their existing employee accounts and simply makes those securely and privately available to virtual worlds to verify identity when creating accounts. (Note: the virtual world would be unable to directly obtain any information from that server other than verifying the person did exist and was on the server's list.)
Standards: data exchange that verifies server and passes data about accounts