render texture assigned to camera now it doesn't render anything at all?

Using Unity Pro. Render texture it seems when applied to the Draw Texture section on cameras it doesn’t seem to render anything at all (all I see is the greyness from the editor window).

Am I missing something or is this a bug?

I followed his guide to the T and it produces the same results:

http://unity3d.com/support/documentation/Components/class-RenderTexture.html

I want to make mention a work around I found for this was just having a different camera as a child of the mainCamera have the assigned render texture and this causes no issues.

However I don’t see why the main camera cannot render to the render texture and still render the view to the screen, especially since this is how the tutorial has worded it to be done.