I have been involved in four discussions in as many days about High Density Hosting. When I ask - what does that mean to you? I usually get a number that is north of 125 watts a square foot up to 200 watts a square foot.
That is one way to look at it, but even at 200 watts a square foot, if your loading up a multi core box with dozens of VM's you will be headed north of that. Typically what happens is that hosting companies balk at the space required to cool 200 watts plus. Looking at power density is about power NOT space.
So in one conversation the company said that they wanted to deploy 10 - 30Kw cabinets. Total draw of 300Kw.If I throw in a PUE of 1.5 I am at 450 Kw for draw. If I have a 10,000 square foot pod that doesn't have a half a megawatt available in either current or generator power, it can be the best space on earth but you can't power it. No power = no CPU cycles, and no company.
Buy power, not space. Think about when the lights go out - you aren't thinking about what a nice neighborhood you live in or what a good investment it was, or how sweet the location is. You just want to nuke some popcorn and watch the Red Sox beat the Yankees.