MicrostockGroup

Found this article at DPreview. 
Thought it might interest the US members :

http://www.aclu.org/free-speech/know-your-rights-photographers

It's been my experience that the lowest paid (and poorest trained) employees in the security field are the least likely to know about photography freedoms. They believe that their badge or shoulder patch gives them the right to tell you anything they want. It's a total power trip for them. My policy is to shoot my pictures where I'm positive I'm in a proper place and to inform whomever is questioning me of that fact and if they don't like it to call their supervisor or a legitimate police authority immediately. I always stand my ground in these cases and make sure I photograph the person who is questioning me.