I read a post earlier today talking about concerns of a healthcare organization that would be sharing its data with its patients. One of the concerns was that sharing the data (with a competitor) would make it easier for the patient to get care elsewhere.
There is so much that is wrong with that attitude. If you have to lock your customers in because they've already got an investment with you (their data in this case), and that is how you sustain your hold on them, then there is something fundamentally wrong with your business model. This is true whether it is the data, or as I often experience in the standards space, an interface (e.g., for lab reporting). What you should be focusing on is providing the best customer service to retain customers, not on "locking them in because you have their data."
If you believe that sharing your data with other healthcare providers will make it easier for customers to leave you, you need to ask yourself who benefits most by the sharing. If it is your competitor, you need to provide better service to your customers, but sharing data only exposes an already existing weakness. If it is you, you have nothing to be afraid of. If it is your customers who benefit most, then you already have the right attitude, and there is nothing to be afraid of either.
So, figure out what it is you are really afraid of, and fix that. And you can start with providing your customers with better service by making their healthcare data more accessible to them as really good first step.