I think you are missing the main problems with this. One, if we have blanket surveillance and look through its yield to find out where to look for probable caus

I think you are missing the main problems with this. One, if we have blanket surveillance and look through its yield to find out where to look for probable cause, how is that different from just not having a probable cause requirement in the first place? (Granted, if you have nothing to hide you have nothing to fear. But that's true if blanket surveillance is flatly legal, too.) Two, this is at least constitutionally questionable, that is, the defense should be allowed to question its legality in court. The fact that they aren't told about it prevents them from conducting a thorough defense. Due process rights should include the right to challenge the legality of evidence, if there is any question about it. Finally, the prosecutors and their witnesses actually are lying when they describe how that evidence was obtained. Do we really want to normalize that and make a precedent for it?