I think in the long run we will use a decentralised/federated system. Privacy concerns aside, it just doesn't make sense to rely on one service or expect one social network to meet everyone's needs/desires.
I think this is exactly how health/medical data should exist. My family should have their own health/medical network node and only my direct healthcare providers should be able to access the data from it and only after I authorize them with a digital signature. Whatever data they generate about my person (or persons in my family) should be owned by me, stored in my family network, and only available to others after I…
More relevant, what happens if you lose access to your data? Or it becomes corrupted? Now, because you owned your data, it's only your responsibility. You know who's not going to put up with that? Anyone who can afford to hire someone else (like a doctor) to keep track of their chart for them so that stupid stuff doesn't happen.
Most people don't realize that many of the connected health record problems have already had high quality solutions provided in the form of VistA (https://www.wikiwand.com/en/VistA). It's interface would make a startup designer cry, but medical professionals find it highly effective. Especially the network effect of being able to hand charts off and coordinate care, which would be very difficult in a decentralized health record world.