Professional when I need to be, but quite playful also.
In many places, it is common for the recording of public property, persons within the public domain, and of private property visible or audible from the public domain to be legal.
In California, Connecticut, Delaware, Florida, Illinois, Maryland, Massachusetts, Nevada, New Hampshire, Pennsylvania, Vermont, and Washington State, the consent of all parties of the conversation must be obtained in order to record a conversation.
(However, the law changes rapidly and any links may be soon out of date.
Signs posted around many bridges, including the Verrazano-Narrows Bridge, state that filming the structure is prohibited.
The legality of such restrictions is problematic; in view of the First Amendment, restrictions on taking pictures of a public structure in public may be unconstitutional, (in view of the fact that prohibiting taking pictures will probably neither prevent nor reduce the potential for such attacks, nor do such prohibitions necessarily mean it will in any way hinder someone from committing an attack in the first place.) The courts have held, however, that in some cases, restrictions on taking pictures on military reservations such as military bases, can be constitutionally valid, so a restriction on taking a picture of a structure that is operated by the military or is on a military reservation might be constitutional, but even then, such restrictions must be reasonable and have some relevant purpose.