You lead a quiet life Herby.
In response to Geoff, I think large scale agricultural growth of cereal crops is a different animal to growing your own vegetables at home. Why are fields ploughed? To turn in the stubble and let the frost get at the soil to break it down into a better medium for seeds to germinate. Gardeners dig to turn in the weeds, incorporate organic matter and to expose the soil to frost. If weed growth is hoed off or suppressed by mulches there's no need to turn it in. If beds aren't compressed by standing on them they shouldn't need to be thoroughly dug over to loosen them up again. As has already been pointed out, digging up crops means they get dug a little anyway.
A couple of other hypotheses behind no dig is that in the natural environment soils have complex, layered structures at which different micro-organisms exist performing different functions and that digging destroys this structure and impairs the health of the soil and therefore also the health of the plants growing in it. Also, that mulches will be incorporated by worms much in the same way that leaf litter breaks down on the forest floor. A final point is that (and I think this has been proven) that digging speeds the breakdown of organic matter in the soil and thus releases more carbon dioxide into the atmosphere.
As I said in the discussion on moon-gardening, just because something has been done a certain way for a long time, it doesn't mean it's the best way to do it.
