In the midst of a delightfully shrill posting we see Ross Mayfield yearning to authorize two vendors he uses to share data about him. What some of us call linking accounts.

Tivo and Netflix Need Each Other: Why don’t they know what movies I have rented or watched? If it’s in my rental queue and I saw it for free on cable, spare us both the hassle.

That’s exactly the kind of thing that Project Liberty and more recently SAML have been trying to enable. One user with two account relationships. Two firms with info about their users. Information they would love to exchange to make those users happier. Serious issues about what embarrassing viewing habits Ross has that he probably doesn’t want getting passed around the internet rumor mill. The firms are just as worried about their secrets.

We can solve this problem. The two firms negotiate an agreement about data sharing. Ross gives his permission to allow his personal data to be shared. Everything necessary to do this is available today. The plumbing isn’t hard. Blocking out the orchestration of the deal is straight forward.

It remains hard getting a legal framework (and that’s what the term circle of trust means) that is robust and reasonable for all three parties.