Sometimes it is useful to have 2 or more UV layouts in a single material. In example - when creating a landscape You can use one UV map for some tileable textures like grass, soil or rock and another UV map for the stencils telling blender how to mix the color textures. As the color textures are tileable (seamless) the first UVmap can overlap the size of a texture image several times. The UV map for the stencil textures must fit the image. We can choose which UV map is used for a specified texture by typing its name in the "Map Input" fold in the Material panel. I've done a scene like the one discribed, and tried to render it in YR. Blender internal renderer does support multiple UV layouts during render, while Yafaray doesn't. It only uses active UV layout selected in the Editing>Mesh fold.