I used to work for a software company, whose clients were all the largest US defense contractors. Once, in a conference room meeting with about 20 important people from a client in the room, I was projecting, talking them through some slide deck. We got to the end, decided to take a break just before noon. I forgot I was still sharing my screen. I answered an instant message from a friend, asking if I could go out to lunch. I wrote, "no, can't. Stuck in this long boring meeting for a few more hours" Some kind person tapped me on my shoulder and told me to stop projecting my screen pretty quick, but not until everyone in the room had read the message. I was reminded of that mistake for a long time after that day.