Israel's Benjamin Netanyahu caught on microphone slamming EU in Budapest...
Conference organizers quickly cut his microphone when they realized his closed-door comments were broadcast... Netanyahu was inadvertently picked up by a live microphone on Wednesday calling the European Union "crazy" and admitting to missile strikes in Syria... After a few minutes it became clear that journalists could hear the comments and the sound was cut. more
People are caught on open microphones quite often.
Rule #1 - If you see a microphone assume it is on. Watch what you say.
Rule #2 - If you don't see a microphone, don't assume one is not there and listening. Watch what you say, until you have had the area swept by a competent Technical Surveillance Countermeasures (TSCM) team.