A published experiment on removing anonymity from records of prescription data in South Korea was 100% successful at identifying 23,163 individuals. For ethical reasons, these were records of deceased people, but there is no evidence living patients have better-protected records. South Korea is not especially weak at protecting health data, it is just easier to tell what is going on. I'm afraid nobody knows what is happening to such data in the U.S. and U.K., although what we do know is not encouraging. There is no question pharmaceutical companies consider this data a valuable resource, or that there are companies specializing in data mining for those willing to pay for results. This is not a simple either/or question, but it is being decided by default. A previous research publication was able to identify 97% of individuals participating in the original Kinsey questionnaires on sexual behavior despite apparently-reasonable efforts to make such data anonymous. None of those people used Facebook, which did not exist at the time. None of them carried smart phones. Many ME/CFS patients have embarrassing medical problems due to no known fault of their own. Many also have financial difficulties. Exposing them to predation by powerful commercial interests, or to irresponsible trolls and hackers, is unconscionable.