(Conventional) Solid state devices are very hard to fail - exception: flash memory
Apart from electron migration issues and failures by excess (voltage/temperature), they're pretty long lasting
Much easier to have a failure because of something else: capacitors failing, oxidation or mechanical failure (for example, because of thermal expansion/contraction)
I've seen people complaining about a dead CPU but I can't find it right now
You are correct. I want to clarify that the failure process is electromigration, not electron migration. It is caused by electrons but it is ions in metal that migrate. Wikipedia has a good description: https://en.wikipedia.org/wiki/Electromigration.
I design integrated circuits and one of the constraints in selecting the width of wires is to make sure that the maximum current density is below the electromigration threshold.
I actually just returned my CPU (Phenom II X4) to AMD, and they've replaced it, but they didn't say exactly why it died. I've asked them for more details, hopefully they can tell me.
Overall though, given with how many computers I've worked with, CPU failures still seem rarer than Memory, Disk, Mobo, or Graphics failures. Of course it ends up being the CPU in _my_ computer that fails -.-
There is still some variance in silicon, so yours may have had a defect that manifested itself after some time, I'm not sure they evaluate returned defective chips to see what happened (and if this is public info)
Also, the packaging is extremely complex and prone to the same kind of defects as other PCBs in the system.
Apart from electron migration issues and failures by excess (voltage/temperature), they're pretty long lasting
Much easier to have a failure because of something else: capacitors failing, oxidation or mechanical failure (for example, because of thermal expansion/contraction)
I've seen people complaining about a dead CPU but I can't find it right now