Mandatory labelling of consumer products enables moral purchasing and avoidance of health problems like allergies. It is mandated in most developed nations, and increasingly in developing nations, especially for food products, e.g. "Grade A" meats..
In China all clothing is labelled with the factory of origin, including telephone and fax numbers. Interestingly, this information is not available to buyers outside China who see only a generic Made In China tag.
The genetic modification of foodstuffs has led to one of the most persistent and divisive debates about the mandatory labelling. Advocates of such labelling claim that the consumer should make the choice whether to expose themselves to any health risk from consuming such foods. Detractors point to well-controlled studies that conclude genetically modified food is safe, and point out that for many commodity products, the identity of the grower and the custody chain are not known.
Voluntary labelling and co-marketing of products deemed desirable is another matter usually carried out by entirely different means, e.g. Slow Food. There has been increased regulatory interest in substantiating these claims, and in some jurisdictions, food labels require regulatory approval before use.
An interesting halfway is those labels that are considered mandatory by one buying population and effectively preclude purchase if they are not there, e.g. kosher, vegan, and the aforementioned GMO-free label now seen on many organic products.