We do this at least once a month.
We select a "theme" in food, make a list and sign up a few folks to bring items for the the basic requirements. Then everybody is free to bring additional dishes.
We've learned not to have too much otherwise we're grabbing people in the halls to come in and finish the feast...

But, there's been times when people were asking the next day: "did you get sick last night?!"

So I stick to the dips and chips...