Not my embarrassing moment, I'm glad to say, but embarrassing for the participants.
Some years ago I was at an industry Christmas party hosted by a major oil company. In past years they'd always booked a hotel for it, but that year - cost cutting I guess - it was held in their HQ, in their large conference/training center. The building was very modernist; all angles and mirrored silver glass.
At one point fairly late in the evening, some people slipped out of the party to grab a smoke. One of them was my lab manager, who promptly came back in, grabbed me and pulled me out the door with a "You've got to see this!"
The door opened into a corridor that ran along inside the outer wall of the building to the loading dock. We were maybe 4 feet above ground level, and the wall, which was all glass, leant outward. Right outside the window was one of my competitors, standing between two cars with *his* lab manager kneeling in front of him with his cock in her mouth. The two of them were looking right at us, watching themselves in the mirrored glass. By the time he had her bent over the hood of one of the cars there must have been twenty people watching.
Just as he got a good rhythm going, though, his boss came flying out onto the walkway and started banging on the glass. They looked sort of puzzled for a moment then suddenly realized what it must mean. The look of horror on both their faces was priceless.
They left without coming back inside, and were both fired Monday of the next week.
Richard