Trouble is, vandalism is so quick and easy to do, difficult to catch, and very expensive to repair! So, I hate to give anybody a reason (like unplugging their Volt) to feel bad. Also, you might already suspect that the Volt owner (charging) thinks that he has a right to park and charge there.
Often, just the parking space arrangement will make it impossible for a "next" car to charge, or even park, awaiting a kind "swap over".
Then, is it an EV charging space, or an EV parking space? Who can tell if the "parked" EV is "awaiting charging" or just using close-in parking?
Perhaps, in planning for EV charging, they should provide two or three EV parking spaces for each Level 2 "charger" (EVSE). In that way, the EVSE could be more easily shared.
However, if one has to pay in some way (swipe a card, etc.) to start charging, the owner will need to actually be there to begin charging his own car.
There is much that needs to be worked out for "sharing".