2) Frequently is a nice general word. I would argue, that it's not nearly enough times to cause an impact on enforcing the law while recording the police has resulted in many outings of abuse of power.

3) If anyone honestly thinks that's a problem, then they shouldn't ever set foot in a court room. Court is all about editing and sculpting the evidence as much as you possibly can to support your case. And again, the benefits of recording the cops hugely outweigh the (theoretical) negatives.

4) It's impossible for a civilian to get a warrant to spy on a police officer. I don't see your point.