Because meta-materials gain their properties from their structure rather than their composition, light bending becomes a practical possibility. Our eyes detect an object because it detects the photons it emits; direct those photons around the object and the object disappears.
So why I hadn't thought of light as a "transformational" media is lost on me.
why the hell do theorists call meta-materials transformation media? It is because of a crucial insight. A material that refracts or reflects light can be replaced by a curved layer of space without the material. Thanks to this insight, instead of trying to come up with a shaped piece of material that will manipulate light as you would like, you can work backwards by figuring out how space must be bent to produce a particular optical response. With that answer in hand, the optical properties of the material can be derived from the shape of space. The importance of this approach is that, if you can imagine something you want light to do, you can design a curved space to achieve that. Optics once unimaginable are now being seriously pursued.