I don't know a thing about porridge. Don't care for oatmeal, farina, or grits either. But, I'll dig into a good metaphor, and with the mushy, soft, sweet mess that is a development team, I have to drool at this one.
Let's just go out on a limb here: 1 is too few, 20 is too many. There is a sweet spot for the size of a development team, and it's somewhere in this range -- the mythical third bowl of porridge.
I only say "1 is too few" because, for me, it is! I can't do it alone, and when I try the end result is unsatisfactory. I'd like to do it alone, really. Social anxiety and ego would lead me in that direction, but a genuine desire to make good products is far more compelling. Obviously I can't speak for everyone because some folks can do it all. There are artist/programmer/executive/marketing chimeras but I will stay out on the limb and posit that they are so rare as to be effectively non-existent. Furthermore, a case can be made that everyone benefits from collaboration. I won't make it here, but it could be made.
So why is 20 too many? This opinion is based on the idea that a certain number of adults can manage themselves as equals and as a team , and accomplish the seemingly impossible. At some scale however, as a manager, I have found that a flat organization falls, well... flat. At that point some form of leadership team and hierarchy becomes needed to perform daily functions, conduct employee reviews, set goals and divide/schedule the work. This is usually when life starts sucking.
When "people" become "resources" a team becomes a factory.
I don't speak to this from ignorance. I've worked in big entertainment factories of more than 3,000 and in tiny teams of 3. A huge team of resources can get a lot done, to be sure. I see the amount of internal friction, need for communication, and sheer number of meetings that go along with large teams, however, saps the process of any real vitality. On the other hand, 2 or 3 people really have a hard time putting out enough volume to self-sustain.
From my perspective, the ideal working team is in the 6-12 member range. I have witnessed small teams of this size pull off miracles of productivity and creativity. My intention is not to come from an "industry" or "indie" point of view, but simply to reflect on what works best for human beings, creativity, and great product. In fact, I'd love to hear ideas on how to make the Third Bowl scenario scale well to larger organizations if anyone has some perspective.
Enough talk, now I'm hungry! What's for breakfast?