Regarding the webfinger idea - there's gravatar.com.
There are a lot of advantages in using such public shared profile services
as gravatar. A user only needs to register - and all his public profile
details become available instantly exactly in the format he desires. For
businesses it would allow
I think a separate profile store would be more flexible. This separates the
user authentication, from user profile.
The user should also be able to configure visibility of profile information.
At a minimum, I think the user should be able to choose which fields of
their profile they want to be
