The running cost is just part of the equation... those servers are depreciating away and generating no revenue!
I'm wondering this, too. The data would still be there, and they wouldn't have to worry about maintenance costs at least, right?
Shutting them down could easily destroy evidence depending on how it's done. EX: Many redundant systems try replicating data from machines that are taken off line. What happens when the full network is taken off line quickly has probably not been tested.
I see, so even just shutting down the servers hosting MU's data could be damaging to the whole network?