Whilst the supply of physical products is significantly improved by reliable product metadata, the supply chain for digital products can not function without it. (publishingperspectives.com)
It can work for physical products such as art, but it can also recognise songs on the radio or programmes on TV. (thebookseller.com)
With physical products, you could probably tell your friends that you had a good experience using it, but it does not self - market. (arcadier.com)