According to iPod touch dedicated websites, such as Apple-touch.com, the last iPod family member is having some problem previously identified as the "Negative Black Effect".
When playing some video, the display delivers a black/dark image.
According to Walter S. Mossberg from Wall Street Journal Apple is aware of the problem and acknowledge it, while working on a fix. It seems it only affects a small number of iPod Touch.
It is nice to see Apple reacting so fast, but it is only when it deals with iPod-related problems, Mac users often have to fight months or even years when it comes to acknowledge a hard