I think this area has a lot of potential. I'm a fan of Atom-based solutions -- the author is concerned about ECC, which is less of an issue for me.<p>Part of the problem with Atom solutions to date was the power-hungry chipset that it used to ship with. The current generation chipsets still consume more power than the CPU, but they are a lot better (~10W against ~22W for the 945GSE vs the 945G).<p>Particularly for solutions that rely on redundant nodes, it's a great solution. In the right conditions you could even move to ambient-air cooling and save a huge amount of energy.
The Arm-based netwinder I had some 10 years ago worked decently as a small web server. His point is really another one, though; about whether it would make sense for big server farms.
<i>If a 4-core, cache coherent version was available with a reasonable memory controller</i><p>Multi-core Cortex A9s are hitting silicon as we speak, so this is actually not far off at all.
It is not quite the same workload or flexibility that the author was looking for, but I was running a web server on my Newton (162 MHz strongarm 110, 4M of RAM) more than a decade ago. Imaging a beowulf cluster of... oops, wrong forum for that particular meme...