I have recently become increasingly concerned over the apparent of “militarization” of the police in this country; I trace this rise back to the events of 9/11. Though the Patriot Act granted sweeping enforcement authority to our federal government, it is my understanding that there is nothing in this law which gives any additional powers to local police.
In the news this past year in particular with the Occupy Protest movement; there have been increasing incidents of police using force, coercion, arrest and confiscation of people photographing and/or recording police. In some cases even journalists have been subject to harsh treatment. As a filmmaker, I find this trend particularly disturbing.
Here is official clarification from the ACLU – It is not a crime to photograph or record police in public while in the process of carrying out their duties when it is done openly and where there is no expectation or presumption of privacy.
Yet even though police have been trained regarding this issue, incidents are still rampant of police arresting people recording them; and in confiscating phones, cameras, film and other the like.
I have seen video of police asking a videographer if their device is recording audio; taking the device from the photographer if answered in the affirmative. From the ACLU:
Another disturbing trend is police officers and prosecutors using wiretapping statutes in certain states…to arrest and prosecute those who attempt to record police activities using video cameras that include audio. (Unlike photography and silent video, there is no general right to record audio; many state wiretap laws prohibit recording conversations if the parties have a reasonable expectation of privacy — which is never true for a police officer carrying out his or her duties in public.) 
Some states like Illinois have passed laws making it illegal to photograph or video police; it is not likely that these laws would pass Constitutional legal challenges under the First Amendment.
With the prevalence of high quality video recording devices in simple cell phones which are carried by almost everyone today, the potential exists for more people to be subjected to the capricious actions of questionable police practices.
Know your rights and be prepared to defend them. Refer to some of the links below, or Google “Photography is not a crime” and follow the links.
Photography is Not a Crime, Carlos Miller, Pixiq.com
7 Rules for Recording Police, Steve Silverman, FlexYourRights.org