I once read that meetings of more than 12 people are undesirable because the personal dynamics of that many combinations of alliances and relationships are too complex.
That's understandable. Getting agreement on a simple proposal can be next to impossible with a much smaller group. Karen doesn't like Ray, Ed wants to control the outcome, Carlos doesn't care about the outcome but doesn't want anything that Ed wants, Harold and Mary are allied against Ellen. You know the drill. Pop in a few more folks and it gets even more interesting.
Extracting the poison of personal animosity and bitter memories can be extremely difficult. Some factions are still fighting battles that started a decade ago. Newcomers to the organization can be baffled by the hard feelings that seemingly come out of nowhere.
It would help if teams adopted a statute of limitations.