Attorney Bert Krages has compiled a helpful guide of a person's rights as a photographer:
The right to take photographs is now under assault more than ever. People are being stopped, harassed, and even intimidated into handing over their personal property simply because they were taking photographs of subjects that made other people uncomfortable. Recent examples include photographing industrial plants, bridges, and vessels at sea. For the most part, attempts to restrict photography are based on misguided fears about the supposed dangers that unrestricted photography presents to society.
Ironically, unrestricted photography by private citizens has played an integral role in protecting the freedom, security, and well being of all Americans. Photography in the United States has contributed to improvements in civil rights, curbed abusive child labor practices, and provided information important to investigating crimes. These images have not always been pretty and often have offended the sensibilities of governmental and commercial interests who had vested interests in a status quo that was adverse to the majority in our country.
Something to keep in mind while you're snapping away at your local Starbucks.