I remember the Rodney King incident was one of the first instances of citizens recording negative police action. Of course, the media pumped up the outrage by selectively editing that tape and forgetting to mention King was driving under the influence at excessive speeds, or that the other passenger(s) in the car was/were not beaten because they did exactly what the police told them to do after King finally stopped the car.
That being said, you take public pay, you cannot complain about being filmed while performing your public job. It is so ironic that cops have dash cams to protect themselves from lawsuits as a result of their interaction with the public, but citizens are not allowed the same protection by filming their interactions with the police.
With the ubiquitous nature of cell phone cameras today, expect the police to keep pushing the 'government obstruction' meme against citizens who film the police doing their jobs. They may even try to get laws passed to make the filming of police doing their jobs a much more serious crime, but even that will not stop the problem. The problem will end when the police no longer act like government paid thugs.