Since modern etiquette has not apparently addressed this question, I guess I'll just have to decline any visits from E-car driving morons.
“If you drive your Volt to visit a friend or relative, what’s the protocol? Do you just assume they’re going to let you plug your car in to recharge while they’re visiting? Do the Volt owners offer to fill up their host’s gas tank in return for a charge?”
You present an interesting canard. If they do come to visit, I would be inclined to not let them plug in without being willing to pay me for that cost. However, if they don’t plug in, then they may be forced to stay and any electric car owner would be insufferable after a few short hours!
I guess I’ll play it safe and just ban them from visiting.