The reason is the 10 years - somewhere in the electronics of the camera, some components (like capacitors, etc.) employ some different materials/process so that it is more environment-friendly once disposed. This is good, except that it means they will quietly fail in about 10 years (of course, from manufacturing date, not from when I bought the camera). The net result is, the camera will soon stop working despite being in excellent condition and, after 10 years, will at least require servicing. A currently 25 years old SLR will still be perfectly working!!!
I am not 100% sure you can classified this as planned obsolescence. It is the nature of the product. ie, the capacitors used only have a relative short life and will fail within 10 years. Just like the SLR will stop working, just much more later in time. It is just the way it is.
Planned obsolescence would be if the camera manufacturer specifically design to product to stop working in a specific time frame. They might do this for commercial, legal or safety reasons.
http://en.wikipedia.org/wiki/Planned_obsolescence