Apple issued an interesting note on the Macbook Pro today, warning not to use palm rest covers or risk damaging the screen when closing it.
To enable thin design, the clearance between the display and the palm rest area is engineered to tight tolerances. Do not use palm rest covers as the added thickness may interfere with the designed resting position of the display.
As a best practice, keep the palm rest clear of any material.
Palm rest covers are quite popular so you’d think that Apple would have thought of the problem, but it seems that Retina Macbook Pro are either going to have to live with it or risk breaking the screen.