Q: In your opinion what do you think the main cause of the Red Ring of Death failures have been?
RROD is caused by anything that fails in the "digital backbone" on the mother board. Also known as a core digital error. CPU, GPU, memory, etc. Bad parts, incompatible parts (timing problems) bad manufacturing process (like solder joints), misapplied heat sinks or thermal interface material, missing parts, broken parts, parts of the wrong value, missed test coverage. Any one or more, on any chip, or many other discrete components, would cause this. And many of the failures were obviously infant mortality, where they work when they leave the factory and fail early in use. The main design flaw was the excessive heat on the GPU warping the mother board around it. This would stress the solder joints on the GPU and any bad joints would then fail in early life.

There are also other significantly high failure rates in other areas, like the DVD.