In Fourth Amendment cases, the Supreme Court has to determine what “a reasonable expectation of privacy” actually is. If you do have that expectation of privacy, then the government needs a warrant to look into your communications. So, if you go out in the public street and shout to the world that you committed a crime, the government does not need a warrant to use that communication. However, if you were to send a sealed letter to a friend containing the same information, you would have a reasonable expectation that the government would not be reading that note.
Because we’re talking about expectations, we have to think about what cultural norms are and the actions that signal what norms are in play. For example, Kaminski notes, “In the 1967 seminal Supreme Court case on wiretapping, Katz v. United States, Katz placed a phone call in a public phone booth with the door closed, and was found to have a reasonable expectation of privacy in the phone call, so a warrant was required for wiretapping the phone.” Closing the door meant he expected the call to be private.
And the problem with frictionless sharing is that it may leave the door open for the government to collect and use information without a warrant.
