Available To The Right Buyer: Sun Microsystems
Sun calls it N1. IBM calls in On Demand. HP calls it adaptive infrastructure.
It is a business concept, not a technology. These business concepts (which are quite good...it only takes a few minutes to sell it to executives) are based on the evolution of IT technologies (grid, automation, web services) and business practices (off shoring and outsourcing).
The idea is that a business only pays for the IT resources it actually uses. It's only a paradigm shift if you haven't been paying attention :-)