Even with the best of intentions things can go wrong and there are lots of unanswered questions in this emerging field. I'm sure the medical organizations involved are very aware of these problems, like protecting the privacy of those in the datasets. We've seen medical data de-anonymised in the past - it's not a trivial problem to solve. Likewise there are moral issues. What happens if you discover X% of people in the study have an extremely high risk of developing Parkinson's? Do you contact them? Do they have the right to know? Do you have the right to tell them? Would they even want to know? These are questions we're only starting to think about now.