This isn't a true etiquette breach, but it was pretty horrible for me!
I hosted a dinner party last July. I invited Dh's business partners and their wives (Don & Marcy and Ned & Linda). All of the guests told DH that they adore Mexican food. DH mentions this to me as I cook traditional Mexican dishes, so we are off and running!
*The day of the dinner, I spent 2.5 hours standing at the counter making enchiladas. I literally didn't move to use the bathroom, get a drink or anything but make enchiladas for 2.5 hours.*
Guests arrive, apps and drinks are served, and I finish up making the rice. At dinner time I put all food on the buffet, call the guests and do all the hostess things that take up about 5-10 mins. My guests are asked to get their food and go ahead and start eating once they sit down. I heard DH rummaging in the refrigerator while I was taking food out of the oven, but thought nothing of it. I finally grab my food and sit with my guests.
Everyone is finishing their dinner and Don asks if there is enough for seconds. I assure him there is plenty (2.5 hrs making enchiladas remember?) I get Don's plate and put a few more enchiladas and beans on it. I hand him his plate and start to sit down when I see him grab a bottle of ketchup. My first thought was, "How did ketchup get on the table?" I was 2 nanoseconds from saying, "Don! That's ketchup!" when I slammed my mouth shut. Don procedes to pour at least a half cup of ketchup all over the enchiladas. He then picks up his fork and tells me how wonderful the food is, how much he loves traditional Mexican dishes etc...
I have had the business partners over a couple more times since then. However, I never fix a meal that requires me to stand for 2.5 hours to make.