Simon Willison defends HealthVault's choice of OPs.
I disagree. It is I, as a user, that should be able to dictate to HealthVault the OPs from which they are to accept identity assertions through OpenID.
Just as I, as a user of Vista, should be able to dictate to Microsoft which software partners they work with to bundle into the OS (I particularly like the Slow Down to Crawl install).
Just as I, as a Zune user ... oh wait, there are no Zune users....
The mechanism by which I (the user) am able to indicate to HealthVault, or Vista, my preferences for their partners is called 'the market'.