In the United States, the First Amendment generally protects the right to record public officials (including police) in a public space. However, there is no federal expectation of privacy in a public street. This means that if you capture a of two people arguing on a sidewalk, you are technically not breaking the law. The trouble begins with distribution.
A hidden camera in a public restroom or locker room is not "publicflash"—it is a felony invasion of privacy. Even in open public spaces, recording someone who has a reasonable expectation of privacy (e.g., inside a changing room) is illegal. Many videos tagged actually violate these statutes, even if the recorder claims they were "just filming in public." publicflash
If using a device that connects via cable (like an SD card reader or micro-USB), bring your own cable. Public cables are often damaged or compromised. In the United States, the First Amendment generally