Like many, I've followed Radley Balko's articles for some time and have a growing sense of paranoia/constitutional outrage regarding false arrest. I think there are a couple of interesting phenomena here. Some folks may not like the two ideas below but I offer them as a conversation starter for understanding what is happening instead of just venting outrage (which is cool too).
1.) Growing ubiquity of recording equipment formerly thought of as "surveillance equipment.” In the not distant past, very small cameras were specialty equipment only available to certain people. In that time, the common thinking was that a person should have some highly-motivated intent for using such stuff because it was very expensive and if you weren't in law enforcement or a PI, then your use was probably not for good.
2.) Law is complex and large, so law enforcement uses some heuristic of propriety instead of actual laws. My impression is that law enforcement people contain a large but not all-encompassing menu of crimes and use some form of pattern matching to compare the behavior of other humans to this menu. Since it is inefficient to compare every rule to each encounter with other people, law enforcement people use the general feeling they get from an encounter to first signal that something is "wrong" and then guide them to a particular item from the crime menu or reach into the foggier area of laws off their personal menu.
Fitting idea 1 with idea 2, it makes sense that there would be an unofficial "war on recording" by law enforcement as the propriety value of the law heuristic is driven in part by cultural values which in turn are slowly influenced by technology. In this case, technology change has occurred more quickly than many people’s sense of probity.