The ‘microphone is always on’ rule has always applied, whether you worked for the media, with the media, or anything in between.
The story unraveling the uber-weird story of ride-share company Uber and an off-the-record meeting, gives us something to chew on. It is a gray area, with journalist Michael Wolff observing (or at least respecting) the rules of engagement in off-the-record agreements, while one of his colleagues Ben Smith does not.
The PR industry makes a better distinction of not just off- and on-the record, but ‘attribution.’ This is worth a read in case you are speaking to anyone, and are tempted to say “don’t quote me on this.”