The art collective WikiHouse.CC has compiled a number of modern concepts - crowdsourcing, computer-controlled machining, and prefabrication - to come up with a Ikea-like method for producing housing. WikiHouse promises the ability to 'print out' your house, and have it shipped directly to you for hand assembly. Their 'about' page does claim to have some engineers on board, but I find the widespread use of plywood for structural support to be a bit wishful. There's no reason they couldn't CNC custom-fit 2x4s from 2x6s like Lincoln Logs. Lincoln Logs, incidentally, were invented as a prefab architecture toy for kids by Frank Lloyd Wright's son. CNC styrofoam blocks could be included for instant insulation; pre-fit conduits could fit together like a bicycle frame for quick electric wiring. They're still a ways from it becoming a viable process, with quite a few rough edges to be worn away on the production side. Prefabricated, unassembled homes aren't unusual, of course. Sears produced thousands of prefab homes sold by catalog, Lustron homes were made from formed steel, and panelized homes are becoming increasingly common. What I think WikiHouse is trying to do is to make the source of the home less singular.
Currently, house contruction is still rather artisan in scope. You have a college-trained architect who puts the plans on to paper, and you hire skilled people to build the home from raw materials using many specialized handtools. WikiHouse exchanges an architect for crowdsourced designs; the artisan carpenters are exchanged for a computer-controlled saw and the homeowner's $20-at-Lowe's power drill. Beams and siding could come from one source; interior walls from another; roofing from yet another. This reduces the scale of what it takes to produce a house by distributing the simplified process across many sources, which is the core of crowdsourcing. In terms of Metrogenesis, this reduces the amount of time and effort to produce a city's-worth of homes. WikiHouse implies that relatively unskilled labor could produce liveable homes in a short time; a team of people trained in erecting WikiHouses could produce an entire neighborhood in a matter of days. Each individual needing a home could select their plans by computer and have it delivered directly to the building site, with little further effort on their part. Making the materials and manufacturing process practical is a matter of engineering. Making communities from prefrabricated downloadable materials is the larger leap of humanity's attachment to ancient definitions of house and city.