If you still have an old iPod Nano, then you have more chances than others to run into trouble. Although the first generation was introduced in 2005, the Nano already ran into trouble more than just a few times, but that doesn't necessarily mean we're talking about a bad player - after all, the iPod Nano became the best selling MP3 player in history shortly after its release, so where there are plenty of sales, some problems will also occur. When thinking about the iPod Nano problems, I think the most notorious are those cases when these players exploded, melted, or even started to emit sparks!

Yesterday, we were talking about one recent explosion proof, and I must confess I was stunned to see Apple had such a quick reaction to this event. Well, I guess they didn't react to my article, but since user reports regarding the first generation iPod Nanos on fire also reached them, it was the right time to do the right thing, and that is replacing for free the defective devices.
In a statement to the press, Apple made things very clear, as you can read below:
"Apple today responded to statements reported by Japan’s METI regarding batteries in the first-generation iPod nanos. Apple has determined that in very rare cases, batteries in first-generation iPod nanos sold between Sept. 2005 and Dec. 2006 can overheat, causing failure and deformation of the iPod nano. Apple has received very few reports of such incidents (less than 0.001 percent of first-generation iPod nano units), which have been traced back to a single battery supplier. There have been no reports of serious injuries or property damage, and no reports of incidents for any other iPod nano model.
Any first-generation iPod nano customers who have experienced their battery overheating should contact AppleCare for a replacement. Any other customers who have concerns about their first-generation iPod nano battery should also contact AppleCare."
Obviously, they tried to minimize the gravity of the issue, but it's good to see them admitting it, although this comes at the end of a investigation by the Japanese government into reports of the Nanos melting and popping open, especially when plugged into a computer or docking station for recharging.
As we were able to see in the last years, this is not a problems limited to Japanese iPod Nano users, since there have been enough occurences of the problem in the US and Europe, too.
For now, it's only the iPod Nano, but I am really curious about the percentage of similar devices from the same period set ablaze by their batteries. I have no information about this for now, but as soon as I hear something, be sure you'll be the first ones to know!