To do this "physically real" is suprisingly tricky; you'll have all sorts of issues with the "white" actually either blowing out to superwhites, or the "white" in your reflections on the floor plane not looking "white enough" and if it does look "white enough" you can't just get that nice "faded reflection" look?
Well, here's where the production shaders can help you. Generally, you use the production shaders (specifically, mip_matteshadow) to apply differential shading to a background plate. I.e. if nothing is in shadow and nothing is reflected in the surface, the color returned is exactly the color you put in. Only when shadow falls is it darker, and if an object is reflected is the color actually touched.
But nobody said the background plate has to be a shot of your backyard. It can just be... well... plain old "white".
In this scene, the "floor plane" is using mip_matteshadow with a plain white color. The scene background is set to white. Traditional lights are used to light up the "CG objects" with traditional non-physical 0-1 intensity ranges. The reflections in the mip_matteshadow material is set to be subtractive, and to fade out over a given distance.
Et voila - you get this nice kind of render that you are used to finding on something like Apple store. Naturally, you can utilize the various Ray Switchers in the production library to allow the reflections in the objects to appear differently (i.e. a HDRI environment or somesuch) while the background still is just "white".
/Z
