I think the larger the head count, the more sternly structured a pot luck needs to be. When we had our annual 4-H potluck, our 'dime-a-dip', what you brought was dictated by your place in the alphabet. What that section of the alphabet brought rotated over the years, so nobody was stuck bringing the same kind of thing year after year. So, A-F brought a main course to feed X number of people, plus serving utensils. G-N brought a side, hot or cold or baked, plus serving utensils. O-whatever brought deserts, plus utensils to serve AND any necessary chilling needs and if it had to be served in a bowl, you had to bring X number of bowls too. A smaller designated group would bring drinks, and the club supplied the plates, eating utensils (if you didn't choose to bring stainless from home), and cups for drinks. Nobody HAD to cook, a store bought or restaurant bought item was fine, as long as it fit your category. It being 4-H, it was expected and demanded that everybody help set up and clean up, and people/families who ducked out of this were spoken to later on. I've been to very few work potlucks, but that's where I've seen the worst cheaters show up and pig out, and where the food categories are way off balance.