Here’s what I’ve come up with so far:
I am me, wherever I go. I may have multiple personas, facets or identities that I use online, but fundamentally, I can manage them more effectively because services are oriented around me and not around the services that I use (it would be like logging into a new user account every time you want to switch applications!).
I have access to my stuff, wherever I am. Even though I use lots of different web services, just like I use lots of desktop applications, I can always access my data, no matter where I created it or where it’s stored. And if I want to get all of my data out of a service into another one, I should be able to do so.
My friends come with me, but continue to use only the services that they chose to. If I can send email from any domain to any domain, why can’t I join one network and then add friends from any other network?
I am the master of my domain. Both literally and figuratively, I should be able to choose any identity provider to manage all my external connections to the world, including running my own, from my own domain. While remote service providers can certainly set the standards for who they allow access to their APIs, this should be done in a clear and transparent way, so that even people who host their own identity can have fair access.