Just because you can do something ....
..doesn't mean you should.
At one client the IT dept were determined to roll out a capacity on demand virtualisation solution for their core retail systems (traditional and online). I explained to them that since the business could easily predict sales increases, because Xmas, BH weekends, etc are fairly regular and new product launches are planned months in advance, there wasn't really a need for expensive capacity on demand technology.
They still persisted, so I asked them if they had a priority structure to assign from which systems the capacity on demand system will take resources from when they are needed. The answer was that they weren't going to do that, they were going to build a resource pool big enough so the capacity on demand didn't have to take resources from any other system.
So they were going to spend a substantial 6 figure sum on a system that would automatically assign resources to a system that already had the resources assigned to it. Doh!!
Somebody tried to argue about the power saving, but we calculated that in the worst of all cases it would at most save £5,000 in power and AC costs per year, which would mean that the system might start paying for itself after 40+ years.
Surprisingly the business saw sense and refused to fund it, although the designer had a huge hissy fit, because he had already started to talk to the vendor about doing case study presentations at various conferences.