Both firms also vow that the customers will have total control over their records—no releases without explicit permission. But the very existence of a detailed health dossier accessible in an instant can make control difficult. What if the government subpoenas the records? What if a potential insurer demands to see all the records, telling you that you can't get a policy if you don't provide them? What if your spouse—or even someone you're dating—demands to see all your records?

While the tech companies entering the medical-record business spend a lot of effort addressing privacy and security concerns, they much prefer to dwell on the benefits of empowering consumers with their own health files. "If you only talk about the risk of these plans, and not the benefit, you're having the wrong conversation," says Peter Neupert, head of Microsoft's health-solutions group. Fair enough—but underestimating the risk would be computational malpractice.

© 2008