MacBook Overheating: Oops...We Forgot a Piece of Plastic

Some MacBook users have found a piece of plastic blocking the rear vent of their new purchased machine. As a consequence, MacBook were running very hot, once this piece of plastic was removed, operating temperatures were back to normal.

It seems that this plastic strip is used at some point during assembly to protect part of the case, and might have been forgotten.
So if you have a MacBook, quickly check that the rear vent are free of any piece of plastic.