One of the many holy grails in data center architectures has been the notion of workload mobility: the ability to pick up an arbitrary set of applications (and their data!), move them over a distance, and do so with an absolute minimum of effort and disruption.
It's an incredibly useful capability, especially if you've got multiple data centers and veritable zoo of applications in your menagerie.
Move apps to get to newer hardware.
Move apps to get more performance.
Move apps to save some money.
Move apps to rebalance.
Move apps because you need to take some infrastructure off-line.
Move apps to increase protection levels.
Move apps because you've got a new data center location.
No shortage of good, practical reasons of why you'd occasionally want to move a set of workloads.
They put casters on heavy appliances for a reason!
But moving applications around has always been a complex and disruptive pain -- lots of planning, lots of coordination, lots of downtime. Not the sort of thing that IT professionals warmly embrace with enthusiasm and passion.
But -- for some IT shops -- that's started to change. And we'll see more in the near future -- I'm sure of it.