Holy moly what were they thinking when they let someone waive their fourth amendment rights? How could any of the sheep we've created be able to make such an important decision?
That is the thinking behind Smith v. Maryland (*) -- if you share information with a 3d party, you have no reasonable expectation of privacy (think about that the next time you talk to your doctor -- HIPPA be damned, the 3d party doctrine has already been applied to medical records (*)).
Smith was rooted in a set of facts where the police were investigating a single person for a specific crime in a situation where they could have definitely got a warrant.
However, by quote mining Smith v. Maryland for that 3d party doctrine, and divorcing that quote from its factual matrix, we end up with an interpretation where the NSA gets anything it wants with respect to information shared with a 3d party. This is true even if the factual basis is the complete antithesis of Smith -- the info the NSA collects is outside a specific investigation, unrelated to any specific person, and gathered in situations where a warrant most certainly would _not_ be granted.
This is how it works in the law. Take some fairly reasonable set of facts and enunciate a principal based on those. Next, divorce the principal from the facts. Profit (if you are fascist).
If you don't think this case will be quote mined, and this principal (that 3d party occupants can override the decision of a 1st party occupant) will become unhinged from its factual underpinnings, then applied to anyone anywhere anytime no matter how innocent -- you don't understand how law works in America. With this case, and your "hmmm -- makes sense" attitude -- you just got robbed, and you don't even know it.