Motivated by a spate of fiascos and consequent legislation, enterprises are currently focussed on ensuring that any privacy sensitive data they may hold about individuals doesn't leak out.
Given the risks of damage to reputation and liability associated with storage of such data, how long is it before enterprises worry just as much about not allowing PII to leak in?
Ben Laurie suggests that one tenet of privacy-respecting identity management is minimalism, i.e. that only that identity information required for a particular application be shared and no more. He describes it as a principal for the protection of the individual - which it is of course.
But, it's also protection for the data requestor/recipient. Unless it has an immediate and (business)justifiable need for some piece if identity information, why ask for it, or even accept it if not requested but nonetheless offered? Or store it past any usage? Better let some identity provider, presumably with a business model and corresponding security technology and processes take the burden and risk.
Just remember to log that you didn't accept it.