At this point, I would not be surprised to learn that: 1) all of these incidents are occuring, 2) the U.S. government (NSA/CIA/whatever) is behind them, and 3)

At this point, I would not be surprised to learn that: 1) all of these incidents are occuring, 2) the U.S. government (NSA/CIA/whatever) is behind them, and 3) the police (local/"federal"/whatever) are aware of the incidents and the USG's involvement and are either actively participating or simply allowing it to happen. If all of the above were true, then all that might be accomplished by going to the police would be that the USG becomes aware of exactly what Appelbaum knows of their actions and, perhaps more importantly, what he doesn't know (assuming there have been additional incidents that he has not discovered). Documenting the incidents as best as he can is possibly (one of) his best course of action(s). I think that I, personally, would also document them publicly in addition to a paper notebook, though.