Apple has recently emailed Apple fans in the US about a recall on the 1st generation iPod Nanos. This isn't the first recall on the 1st generations Apple has done, it has already been recalled in Korea, Japan, and some other countries. Anyways, turns out the 5 year old 1st generations have a potential battery problem. In rare cases the battery may overheat and may leak toxic battery juice or explode causing harm to the user. Right now, Apple is offering a replacement program free of charge. More information about this can be viewed here. From there you can verify your serial number to see if you qualify and to initiate the replacement process. The 1st generation iPod nano has a white or black plastic front with a silver metal back.
The email tell you if you got any questions about it, you can visit the Apple Store, but from my experience yesterday, they were no help as the employees had no idea there was are recall. I seen some comments on other websites with people saying employees from other Apple Stores told them to go home and initiate the process online as they have no replacement stock handy. There is no use calling Apple Support either because I just did and the support guy did not sound sure at all when he answered the questions. He asked me if the email I got said it was free... Nothing better to do but wait.
Since the iPod Nano model is currently on the seventh generation and Apple has discontinued the 1st generation for several years now, it is unclear what model Apple will send as a replacement. The replacement process will take about 6 weeks. If you have a personalized iPod nano, you will get a non-personalized replacement.