https://www.schneier.com/blog/archives/2014/12/the_limits_of_p.html - "The next time you call for assistance because the Internet service in
your home is not working, the 'technician' who comes to your door may actually be an undercover government agent. He will have secretly disconnected the service, knowing that you will naturally call for help and -- when he shows up at your door, impersonating a technician -- let him in. He will walk through each room of your house, claiming to diagnose the problem. Actually, he will be videotaping everything (and everyone) inside. He will have no reason to suspect you have broken the law, much less probable cause to obtain a search warrant. But that makes no difference, because by letting him in, you will have 'consented' to an intrusive search of your home"