Apple has released a support document which tells all MacBook Pro users to remove all palm rest covers. This is because the space between the keyboard and the screen is even less than the previous gen MacBook Pros (so they can make it thinner). Apple Notes:

Leaving palm rest covers or other material on the palm rest surface of your computer could result in damage to the display when you close 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.

Apple has now seen MacBook Pros with this problem and they feel that all should be removed to prevent further problems.

[Via Macgasm]