Carlos Miller at Photography Is Not a Crime coins a term (at least it is the first time I have heard it) for certain arrests called "contempt of cop." I think it is a great term that summarizes a whole class of actions that many police officers treat as crimes, but in fact are no such thing. People are getting arrested in public spaces committing no crime every day in this country for charges like "failure to obey" or "photographing a police officer." Police like to feel like they have absolute authority on the streets, that they are mini-dictators of the patch of ground within their field of view. This is a fantasy, but as with all fantasies, folks get really upset when other folks try to dispel their fantasy.
The scary part is that the few who get off quickly are generally the ones who have had their incident video-taped. Which is probably why police are working so hard to try to make photographing and videotaping of police illegal. Because they know that in situations of he-said-she-said, the cop will win down at the station and among his buddies at the DA, particularly if his fellow cops will, as is typical, fabricate corroborative stories. Citizen video tends to break this power imbalance.
One of the most notorious contempt of cop cases to make headlines was last year's arrest of an Albuquerque TV news videographer. Because that incident was caught on video, charges were dropped against the videographer and the cop was terminated.
That incident also prompted Albuquerque Police Chief Ray Schultz to issue a new policy stating that officers were not to arrest people for "refusing to obey" unless that person was already being arrested for another crime or physically keeping the officer from carrying out his duties.
Defense attorneys derisively call the refusing to obey charge "contempt of cop" and claim that APD routinely violates residents' First Amendment rights when they use it.