Comment by TeMPOraL

Yes, but that's not a strict division, and relies on anyone's understanding who has what privileges, where did the information came from (and if it came from where it claims it had), and a host of other situational factors.

'simiones gives a perfect example elsewhere in this thread: https://news.ycombinator.com/item?id=43680184

But addressing your hypothetical, if that note said "CAUTION! Bridge ahead damaged! Turn around!" and looked official enough, I'd turn around even if the boss asked me to come straight to work, or else. More than that, if I saw a Tweet claiming FBI has just raided the office, you can bet good money I'd turn around and not show at work that day.