At least twenty years ago, I was involved with a secular Jewish non-profit agency which had their big convention on the west coast that year. Since about 10% of the delegates were Orthodox (modern), this organization had begun serving Kosher meals; initially just to those who ordered them and subsequently the entire convention was kosher.
So that year, for the first time due to a lay person macher, the Orthodox Union(OU) was hired to be in charge of kosher supervision at the hotel.
It was Friday night and about 150 frum delegates had their seperate seuda in one room and in a much larger room were several hundred other delegates with their program and meal.
Anyway, at the start of the seuda, an agency official who was with the larger group comes running in to see me and is all excited. This fellow is ranting that the OU is not allowing the food to be served and that I should take care of the situation.
I spoke to the Rav Hamachshir and he indicated that the group insisted on having the microphone on and he refused to serve the food under these conditions. I asked whether this made a difference to the kashrus of the food and if this was OU policy.
The Rav Hamachshir (who later was responsible for the entire OU west coast kashrus) explained that the Chillul Shabbos put a P’gum in the food and OU policy for this situation was created that night.
Anyway, the program (with mike) waited until after the food was served.