The logo was translucent and also allowed light in from the back. There was a logo-shaped burn issue but it was caused by ambient light shining through the logo. At least that's how I understood it.
+1. I can imagine someone leaving the laptop in full sunlight, and it burning through the logo - but it feels more like user issue, you don't leave electronics out like that.
Edit: https://discussions.apple.com/thread/3476393