Besides equity and the central issue of environmental quality, I left this comment at Market Urbanism:
...my major concern about the idea of "...likewise provide a regulated built environment through voluntary private contracts." is NOT that I don't like the idea. In fact it's fine. The "least intrusive means" should be always kept in mind. The only issue for me is the huge transaction costs which, I believe, make private agreements for land use quite impossible. Thed very reason we have government is because "voluntary private contracts" are too complex. We got rid of tort law (as to land use) because it was much easier to have uniform area-wide regulations.
In short, I simply don't think it can be dome. Too complex. Too much transaction cost.