I was a bit disturbed this morning when I sat down on the porch with my MacBook and saw a strange bright blob in the middle of the LCD screen. I thought the display might be damaged, but when I moved the laptop the spot went away.
Then I realized that the spot was actually the light of the sun, which is so bright that it is shining through the translucent Apple logo on the back of the lid, and illuminating the centre of the screen from behind. (Normally the logo is lit up the opposite way, by the lamp from the LCD panel.) I guess you could call it a design flaw.