[mch929]

Based on what I've seen in my experiences with building my own computers, the cause of fan noise in computers is not so much a necessary evil in our age of faster processing (old CPUs like the Pentium 4 ran hot as well), but rather a simple hardware problem due to the fact that many computer manufactures use cheap/noisy small stock fans. Replace a computer cooling systems with a slower-rotating larger diameter fan, and you will most likely have more airflow with less noise. Obviously that solution would be harder in space-constrained laptops, but I imagine with some clever engineering (ex. having large fans blow out the bottom of the computer) the designers could work out those issues if they really had the money and inclination to do so.