History:
I was configuring our production Nexus 7000 today and was also moving some modules around in order to accommodate better cabling options.  The one problem that I had with our Nexus switches initially was insufficient 110 power leads in our lab to power them fully.  Today I was able to resolve that by acquiring C19 pigtail cables to power al the power supplies on just 8 outlets (needed 12 to run all the power supplies). 
Philosophical:
What I have also done was move a few modules around in the chassis that where originally powered-down in order to run the chassis.  What I noticed on the Nexus 7000 now is that you are able to poweroff a module even though a module in not installed:
     N7K2# sh run | inc power
     poweroff module 1
     power redundancy-mode combined force
     N7K2# sh module 1
     N7K2#
As you can see there is no card installed in Module 1 but yet the power is disabled to that module. 
I am trying to figure out if it is a safer option to keep the module powered-off for security and sanity or is it better to leave power to that slot.
Current Direction:
For now, I am going to leave the power-off to that slot in order to
     1) Prevent anyone from adding a module in the future
     2) Also prevent a sudden power draw that could have a negative impact in the future (exceed power requirements)
     3) Keep people honest – ensure a change will be submitted if more capacity is ever needed