It's technology transfer straight from those rapid prototyping machines which 'print' layer after layer of plastic to form solid shapes. For plastic read concrete. Apparently it's called 'contour crafting' and, as with the original, you can build any shape you like. Greg Lynn must be ecstatic.
The Register claims that plumbing and electrics can be fitted as the printing goes along. And that a 2,000 square foot two-storey house can be erected in a day at one fifth of the present cost.
You worry a bit about how you do steel reinforcement and, given the normal behaviour of two-storey-high wet concrete in its first 24 hours, formwork. But hey, these are just details.
Take a look at the Contour Crafting site and wonderThe most cogent of many comments posted on the system runs '.24 hours?. But it'll still take 5 years to get planning permission.'