Ekopedia, an online encyclopedia of environmentally friendly alternative techniques, has a very good summary of earthbag building. I’ve quoted a few passages below.
More and more people seem convinced that earthbag combines the best of the past and the future. Earthbag is a hybrid earthen masonry material. It combines one of the most basic building materials, subsoil, with a very tiny proportion of manufactured metal and inert plastic. It has very low embodied energy content.
It can be built by almost anyone, and is non-toxic. It encourages group cooperation, relies on local resources, and requires only hand tools and inexpensive supplies. Yet it provides a sophisticated inter-connected structure with both tensile and compressive strength. And, as a final benefit, it is bulletproof…
Earthbag appears to also be uniquely suited to high seismic risk regions. Like complex systems designed to allow multi-story buildings to flex, earthbag’s low-tech matrix of strong poly bags and barbed wire may dampen damaging horizontal motion during an earthquake. Just as soil-filled geo-textiles have replaced stiff concrete for site retaining walls, this new technology may revolutionize architectural construction…
Earthbag may become the material of choice for owner-builders in hot and warm regions, and in places where labor is less expensive than materials. With light-weight fill it may become competitive in temperate regions as well.
You can read the rest of the entry at Ekopedia.