There was a recent thread (long) on the protocol of leaving one's car plugged in at an airport. I'm not sure whether there were any conclusions drawn, but there seemed to be a split between the subsistence-charger (don't take more than you can eat) and those who felt that chargers were first-come-first served. I don't want to restart that thread. What I wanted to do was share my experience from yesterday evening.
I drove out to Stone Brewery knowing that they have 2 EV charging spots. One was occupied by a white LEAF and the other unoccupied. I pulled out my trusty J1772 adapter, plugged in, and went inside for dinner. After I sat down, I opened my PlugShare app, checked in, and noted about how long I would be so that if anyone needed the spot, they could let me know.
When I got back to the car, I saw this:
So, I unplugged, moved the cable over and plugged it into the open charge port of the black LEAF. It is one solution to sharing chargers when there are more EVs than places to plug them in. This was a very pleasant experience because whoever wrote this note put an exact duplicate on both my Tesla and the white LEAF still parked next to me.
There are times when reacting to someone else's need for a charge is impractical -- like when you're plugged in and have traveled to a different continent -- but for common cases, a short-term tech solution exists in PlugShare and the low-tech solution on scraps of paper and a "thank you".