I think I disagree somewhat with the premise of this article. Computers are more efficient in general when they are fully loaded. A home server is rarely fully utilized and doesn't realize the full potential of multitasking/virtualization. It is more efficient to share different tasks among the same set of disks and memory. On the cloud, anything you didn't use could theoretically be given to someone else.

The hardware lifecycle should also be considered. Although home environments often recycle equipment, cloud environments are in a better position to get more bang per watt, and can upgrade their SAN storage capacity easily to handle changes in demand.

I suppose there is a lot of inefficiency in hitting all those switches and routers on the way to a cloud's network. However that's shared with other users as well.