Hopefully the world of electric vehicles has its own book of unwritten etiquette!
....but.....as I found out when one of those new Leaf owners asked me to unplug the ac charger he had temporarily plugged in when I had finished with the chademo, and plug the chademo into his while he disappeared off on a walk, the car can lock the cable in place.
You can stop the charge on those chargers by simply touching the stop button on the screen, so the petulant gesture is always available for severe offenders without resorting to potential vandalism.
I think over 1 and a half hours spent on the charger is a bit over the top, but those Leafs have larger capacity batteries than mine (40kWh, rather then 24 kWh), and contrary to the best advice for preserving battery life, they were charging it to 100%.
Here's my little Leaf. Getting quite used to it now, and in spite of being on the edge of civilisation in rural Northumberland, and currently it being our only car, so far it's suiting us fine.
The totally free fuel is going to last until April when NCC may start to charge for the 20 or so rapids, but the 7kW chargers may escape. After that likely to hit the 1/4 the cost of petrol/diesel level.

- the nice colour and the shiny ears are growing on me nf own work
Regards Neil