If we could apply big data techniques to medical problems, we'd learn a ton of interesting things.
"Is tinnitus worse in louder cities?"
"Are people who live within X miles of oil refineries more likely to get cancer / parkinson's / whatever?"
"Do people with a history of anxiety develop tinnitus at a higher rate?"
etc. If we could get everyone's data into a single database, we could learn all kinds of fascinating things. Two big problems:
* data security. Medical information is considered by most people to be way more private than almost any thing. Even if you are trying to convince people to share some data in a safe and quasi-anonymous way, and even if you're doing so with very altruistic reasons about wanting to cure diseases, most people are going to be very skeptical.
* what you might find. This is me being cynical, but, if you really had all this health info at your fingertips, you would be able to very quickly and very convincingly demonstrate that various industries and even specific chemicals have very specific and dangerous consequences for people / communities. Many people would not like this because it would be bad for their bottom line. We all know that, for instance, coal plants are terrible for the world, but the easier it is to tie that to concrete facts like "if you live within X miles of a coal plant, you're going to die Y years earlier", the more likely people are to loose their shit over it.