The three permaculture ethics of "earth care, people care, fair share" is a topic that sometimes raises eyebrows.
Everyone agrees that caring for all life on earth, as well as people, is a perfectly noble goal. But "fair share" makes people think of communism at worst, or redistribution of wealth at best. The phrase brings to mind taxation and other forms of forced confiscation of property by a government with threat of violence. It once seemed uncomfortable to me that this negative feeling would be associated with such a positive ecological movement.
To force people at gunpoint to give from their excess goes against everything nature teaches us.
Therefore, when I teach permaculture, I prefer instead to demonstrate this using something we all understand: the backyard vegetable garden and/or fruit orchard.
Everyone who has every produced food in their backyard knows that they can easily (and accidentally!) produce an abundance beyond what they can consume. Therefore, everyone shares their extra produce with their neighbors, and they feel great about it. That good feeling you get from sharing stands in stark contrast to confiscation.
I think that it is this spirit of generosity in sharing that is so neatly encompassed in the idea of "fair share", and understood in that spirit, it becomes clear why "fair share" is one of the three main ethics of permaculture.
We don't want to produce waste, and we want to care for the people around us. If we are not freely sharing our products with those around us, we are greatly limiting ourselves and our community.
In sharing out of our production, we are exponentially increasing the benefits of our work. Instead of a bunch of tomatoes rotting uneaten in the field, they are being enjoyed by everyone we know. Those people, in turn, are enriched by our sharing and they can then take the benefit and "pay it forward" on to yet more people. Eventually, I believe, this "energy" that's been shared finds it way all the way back to the original giver, in one way or another.
Anyway, those are just some thoughts I wanted to share.