I searched for this article about how much land it takes to feed a person so that he can be self sufficient.
Self Sufficiency
It's about 0.1 acres per person (Of course you gotta also combine your acres with 3 other person to be effective).
It's a rough estimate with room to improve by using better methods or better grade seeds and stuff.
Some people live in deserts and stuff, and some of us don't even have enough land, so it won't be feasible but still, can such a concept ever come to be? Maybe should start one a program for retirees to tryout. Some where outside cities. I wonder if there's anyone out there who's doing it.
I've heard of some wild projects out there about 'modern' farms where the crops are grown in towers to save space.