I think an interesting follow-up to this since it's now 8 years old, would be an article on setting up DHTs in the cloud, like on Amazon's EC2. As demand for the database/application goes up, rolling additional nodes in real-time would be pretty snazzy. It would 'seem' to me that most use cases need a redundancy level of 3 per location, and then spread across three locations. The capital costs of physical equipment, racking, zoning within a facility for redundant power etc. make a cloud solution much more interesting for 99% of use cases.
