We have to do a lot of formal (and informal) entertaining due to my husband's job and have a huge store of dinner party stories. sometimes the entertaining is compulsory (ie: bosses, company colleagues etc) and sometimes it simply fun (having people round because we "owe" them and it's our turn) and sometimes by blackmail (there was a tradition of "gnoming").
The worst one I hosted was a dinner for a group of young men and women about to finish their training course (my husband was on the staff at the training establishment). Please bear in mind that social etiquette is actually part of the course they were on.
Firstly, only one of them sent an acceptance to the invitation although one of the females (three males, two females were invited) left a message on my answering machine an hour before dinner telling me she hoped the food wouldn't be "...fattening as she was on a diet...".
They all arrived together - half an hour late.
Menu was Watercress Soup with homemade sourdough bread, Duck in a whisky and cream sauce, Chocolate and Chestnut Souffle followed by cheese and port etc.
I served the soup and took my seat. Cue one of the male guests expressing surprise that I was joining them for dinner - "Isn't this only for personnel?". Then one of the other male guests took a spoonful of the soup, tilted his spoon to let the soup drip back into the plate proclaiming "What exactly is this?".
One of the females was so quiet that I never heard her utter a word all evening and she didn't even reply when I tried to draw her into conversation. The other female was so loud and abrasive and talked over my head throughout dinner.
Third male guest pinched my backside as I cleared the table after the starter.
During the main course, the male guest who'd expressed surprise at my daring to sit down and eat, proceeded to lecture my husband about his job and correct him on various points he felt were salient and to tell the colleague (and best friend of my husband) who had also been invited that she didn't have a clue about things.
Then he asked my husband about their placements after training - when my husband told him that it would be decided partly on his recommendation, guest said that the trainees had decided that they wanted the list in advance and would "...divvy it up amongst themselves...".
Over dessert, I ventured an opinion on some current affairs topic that was being discussed only to be told by strident female that she was surprised I'd even thought about it - "...isn't it a bit out of your depth?"
By the time they left - we practically threw them out as quickly as was decent - I had smoke coming out of my ears, my husband's colleague was aghast at the thought of working with them and my husband was composing a strongly worded letter to the instructors on their behaviour.
Three of them never bothered with a thank you note (and they never brought a gift) and of the two who did send a note, one addressed it to my husband, thanking him for organising caterers!
On the flip side, we did attend the world's best dinner party during our time at the training establishment. All the staff lived on site and one of the bosses organised a Safari Supper - drinks at one house with one set of guests, starter at another house with a different set of guests, main and dessert as starter and then everyone back to the bosses house for cheese, port and brandy. It was an utterly fabulous evening - not everyone on the staff chose to take part and there were lots of people semi-drunkenly cycling around the patch between houses as they made their way from one course to the next (occasionally knocking on the wrong doors!). It was in our first couple of months there and it was a great way to get to know everyone.