The structure christened by the biologist Garrett Hardin in Science in 1968, whereby if a good such as a village common or an area of fishing is held by in common by a society, there will be a tendency to over-use or exploit it. Each individual gains the full benefit of herding an extra animal, or taking an extra cargo of fish, whereas any loss is borne across the community. Any individual can also argue that if the others exploit the resource he had better do so as well; if the others do not, then it will do no harm for him to take a little more. The inevitable outcome is the eventual destruction of the resource. Although the structure is usually taken as an argument for private ownership and against communal control of assets, anthropologists have countered that in all societies in which there is communal control of a resource, norms against individual exploitation of it prevent the tragedy from unfolding.

http://www.sciencemag.org/sciext/sotp/commons.dtl#essay Hardin’s ‘The Tragedy of the Commons’, with updates and responses

http://www.garretthardinsociety.org/info/links.html A list of internet resources on Hardin’s work