This is horrible. I don't know if Apple always was like this, but this whole situation stinks. It seems they'll do anything to earn themselves an extra penny.
Hey dimwad...it's a third-party component, not Apple's doing, and battery overheating has been every manufacturer's problem when it comes to Lithium-ion batteries. Only recently, with the help of electron microscopes was it found how this kind of overheating comes about.
With use, the lithium forms micro-small crystals that can grow and puncture the ultra-thin dielectic in the battery. This then forms an internal short circuit and the extremely high energy-density of the lithium-ion battery is released, causing the heating.
This was a totally unforeseen problem of lithium-ion batteries, and once the problem was recognized, batteries were redesigned to reduce the problem. Without changing the materials in the batteries, it is not 100% guaranteed to not happen.
Different materials and new manufacturing methods are on the way. The current density requirements of batteries for the portable market are amazingly high. We all want our devices to go a long time between charges and we want the battery to do a lot when they are being used.
You could probably only need to fill your jeans pockets with enough iPod Nano batteries to start a car. That's how powerful they are. As consumers, we really don't appreciate how much different an iPod battery is from an equally sized AAA Duracell.
Yet 15 overheating iPod out of tens or hundreds of millions, is an incredibly low failure rate. A person has a much higher probability of going into the hospital with a minor problem and coming out with a life-threatening infection you caught while there.
Starting about the time the MB Air was put on the market Apple began to make their own batteries, so only with the latest models of products is Apple the battery manufacturer.