According to part two of the series on Health 2.0 in Modern Healthcare, barrier to Health 2.0 include: an age gap (Health 2.0 appeals to a younger demographic) and privacy according to David Brailer. Privacy is a big concern because these sites are not covered by HIPAA and contain lots of private health information although one's identity can be hidden. Even without creating an account in sites such as, PatientsLikeMe.com, one can view detail about symptom status and drugs for individuals with ALS, MS and Parkinsons. But this appears to be a trade off many patients are willing to take.
Can these site be hacked? Have they already? To what extent are they being using for targeted advertising?
One can only hope that users read the site usage policies before plunging into revealing their disease status.

Technorati: Health 2.0