In the link you give, Peter Williams writes: "...

In the link you give, Peter Williams writes: "The identity provider would, of course, understand that all these single use identities are really all part of the same identity." That's the problem with the the SSO that really interests me: the UK government's ID card/ID database. The identity provider is the *government itself*, and so would be able to link all those disparate identities together. Each department might think they were separate, but the security services certainly wouldn't....