Basically, it should be clear that all data connected to a person is irrevocably theirs. Any provider can build services for taking advantage of the data -- but it'd be the user's right to migrate it at their pleasure.
We need something like what happened with OpenID and Oauth. OpenID may be gone, but one company made a few bucks on it and OAuth is largely inspired by it. Someone needs to find a way to make a buck moving profile data around in a meaningful way then that becomes a de-facto standard that gets copied and used all over.
Then the government can regulate something that already exists rather than regulate something shitty into existence.
Of course this wouldn't lead to any magical inter-operation of services, but that wouldn't be the point anyway.
I think this would be absolutely brilliant. The ability to readily move data from one service provider to another would provide a much-needed boost for competition in the digital space.
I don't know how common it is, but at least in Finland one can move their mortgage from one bank to another if they get a better deal elsewhere [1]. Or, one can move their mobile phone subscription and keep the old number. I find these kinds of service transfer entitlements essential for efficient competition.
[1] Or technically: one can always pay their Euribor bound mortgage off without extra cost, and take a new mortgage from another bank.