An interesting comment in US v. Jones
In case you've forgotten, this particular case related to the government's right to place a GPS tracking device on someone's car. The court ruled that this particular use of the technology was indeed an infringment of the person's Fourth Amendment rights, which was an interesting ruling. But here's what Justice Sotomayer said that I found particularly notable:
More fundamentally, it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties. E.g., Smith, 442 U. S., at 742; United States v. Miller, 425 U. S. 435, 443 (1976). This approach is ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks. People disclose the phone numbers that they dial or text to their cellular providers; the URLs that they visit and the e-mail addresses with which they correspond to their Internet service providers; and the books, groceries, and medications they purchase to online retailers.
I'd say that that's a good idea, and one that definitely needs to be considered more carefully by the courts.