I think Upwind has a good point here as I can see both sides of the problem. My brother lives near the proposed site of one of these eco towns, and he is not happy since he likes to live in the countryside and it is a lovely environment. So I agree with him that it shouldn't be built.
However, I live in a city and, much as I would love more open space here, I find that houses have been demolished to built blocks of flats and the size of housing in cities seems to be smaller and smaller.
Why should city dwellers be confined to tiny spaces, when rurual dwellers are able to enjoy such a lovely life style?
However, I also believe that these "ecotowns" would be built to the currently appalling standards of most newbuilds with a tiny backyard and paper thin walls. So really, we are just creating cities in the country.
FWIW, I don't believe that they will be built at all as with house prices falling, housebuilders are battening down the hatches and won't want to be involved in building loss making estates.