I don't see any technical limitations preventing that. And I think it's a desirable feature. Imagine a world where you don't have to come up with lots of passwords and sign up on dozens of websites, but instead have one identity that's saved in your device and you can access any free software service without signing up and it'll already tell you if your friends are there. It could interconnect content and features...
It's a bit difficult to get it right, though. The identities need to be secure and reliable. Servers can't vanish (or data needs to be distributed) or people will lose everything at once. We need pseudonymous handles, sock puppets and access control. And there is a lot of trust involved. We need to mitigate for spam and trolls...
And agree on one standard that gets everything right for any arbitrary use-case.