A tech guy can ask a non-tech guy if he can examine his phone. If the binary on the phone differs from any binary the tech guy can get by compiling clean source code, he can raise questions. This is how a group of tech guys who are in communication with each other can protect the privacy of a much larger population of non-tech guys.
Right; if you don't understand the technology (or like most of us, haven't taken the time to comprehensively review it) you have to rely on social proof.
