IMO, the Court got the ruling Right, but the underlying principle wrong. We routinely entrust our private information with third parties, intending to keep that information private, and not intending to forfeit our 4A protections of this information from arbitrary invasions by the government.
We enjoy “privilege” in sharing information with doctors and lawyers. This protection should be expanded to any professional with whom we share data to help us manage our lives, including cell phone companies who are providing us digital file cabinets, and DNA companies who help us interepret our DNA.
Essentially, the information is ours, not the professionals’. That we are storing it at the professionals’ places of business, and not in our homes, does not lessen our ownership of the information, or our expectation that it will be kept private.
Searching that information should require a warrant, ensuring that the government is not being arbitrary, and not just casting wide nets in the (mostly vain) hope of catching criminals. They must have probable cause to believe that a crime has been committed and that, in the limited number of places they have specified that they will look, they will likely find evidence of that crime.