Looks like the 4G iPods suffer from quality issues (something I thought to be impossible with Apple products):
"New fourth-generation iPods are making their way into customers' hands, but some users are complaining about smears, scratches and blemishes on the music player's case. Some customers are discussing the problem at Apple's support discussion forums. Users are providing a wide range of descriptions of their iPods' blemishes, including a light brown stain, worn plastic, scratches, brushed marks, and visible smears."
Read the full article at
Think Secret.