I work in this space in the private sector. From my perspective, the greatest impediment in the U.S. relates to our laws regarding PHI. I work on a system with petabytes of medical data -- but researchers can't access it because our laws and regulations don't support it (and thus provide no financial incentive and only risk and lawsuits for the companies holding it.) It's abysmally sad.
Well, PHI protection (HIPAA) is actually a good thing and doesn't really prevent researchers from accessing data as long as PHI is stripped (de-identified dataset). Now getting that de-identified data is not always easy...
