The DOs that we have organized have been either one of two types: A. Those where everybody paid as they went, including at a couple of fairly large dinners; or, B. Those where we had intended to pay for everything from the beginning. To the best of my knowledge, both types worked perfectly, although there may have been some minor issues at individual tables in the pay-as-you-go situations, that never came to my attention.
I have, however, attended numerous DOs where the organizers came up short and, as a result, the organizer or other responsible attendees have had to pitch in to cover the shortage. As a result of these experiences, I would strongly advise any DO organizer who is faced with a cover charge at a restaurant or on a tour bus, to insist on full payment from all attendees prior to the event, unless you really don't mind picking up a shortage.
Missy is absolutely spot on that the only way to organize DOs successfully is as a benevolent dictator--"This is what I have planned and this is how much it costs. If you want to come and enjoy, you are welcome. If you don't like my plan, stay home, and make a plan of your own."
Sure, there are attendees who will moan and complain about one thing or another, but that is their problem. The only time that an attendee has any reason or right to complain is if the the organizer blatantly misrepresents the offer. For example, publishing that an activity will cost $20 per person and then, after you have participated, requiring a payment of $60 per person. That has also happened, and it is just so not cool.
I will admit that we were much more Pollyannish in our early FlyerTalk days, treating everyone we met on FT like someone who would become a wonderful good friend. We got burned a few of times by folks whom we had treated with completely open honesty and hospitality, but that's ok. We have also found a few princes and princesses, and we are old enough to know that kissing a few frogs before you find a prince, is still a good investment.