Why are you so sure the data remains private? Has Apple never handed data over to the gov. for investigations criminal and otherwise? Some of the genetic companies hand data to the FBI. The reason is great and moral, tracking down serial killers and the like. But, still, regardless of how good the proximate reason, the overarching trend is not so great.

And yes, I'm sure all the telecoms, hospitals, etc. also hand over our data. Adding one more, much more comprehensive data source to the pile doesn't help anything.