I don't think anyone is suggesting self hosting of profiles, just to go from one provider to many providers. That would involve interoperability. The advantages

I don't think anyone is suggesting self hosting of profiles, just to go from one provider to many providers. That would involve interoperability. The advantages of this are many, no service could just query one host and get all profiles that cross their path. A user would explicitly give pandora or Microsoft access to their profile by providing something like their email or some similar identifying string that could be tied back to the host of the profile.