I think its a great idea.
It does happen informally here in France as I'm sure MAK knows. Traditionally, in the areas I've lived in, people grow as much as their land can support and they have time to grow. Then it is distributed amongst the neighbours and friends. My 82 year old neighbour is out on his tractor most days tending to 2 acres of veg which he will donate to the elderly and to the local nursing home.