> Smith voluntarily transmitted the phone numbers he dialed to the phone company, information he and everyone else know are commonly stored as business records

I think I can understand and agree with this. I'm not sure what I think about the phone company disclosing these records to other people. Regardless of its actual legality, I think the distribution of that data could be a breach of trust.

It is entirely reasonable for my phone company to know who I'm calling, but I still expect that data to be "relatively private". I would be upset if my neighbours could get it from the phone company. I would be upset if the phone company mailed that data to me on a postcard. I think we should be similarly upset if the police can get hold of it without a court order.

How does the law address this? Is that information just not disclosed "in confidence"? Does the law follow a "genie out of the bottle" logic, whereby information that is not absolutely private is not private at all? Or do law enforcement agencies have a privileges regarding otherwise private information?