[Charles Martel]

I'm pretty sure the connection to Fry's power socket was done without permission. The slug even left the weatherproof cover open as he slinked away in his plug-in. Thief.

I've got a hunch that someone out there has started a listing of unattended, hot AC outlet locations. Sort of like the "wardriving" WiFi lists.

Back around 2004 or so, two of those glorifed golf cart type plug-in electric "urban cars" began appearing in my office building's garage. The drivers would arrive very early and park in the spaces by the wall outlets. After a month or so, the weird little cars were no longer seen.

One day I mentioned it in passing to one of the building maintenance guys, who informed me that the management had noticed it too and they killed the power to those outlets. It wasn't so much the electricity cost (a drop in the bucket, in those circumstances) as it was the fact that the drivers didn't ask permission or offer to pay. So, no more electricity for them.

[Myrddin]

It's a drop in the bucket for an occasional thief. Not so if lots of vampires appear on your sockets. Getting a policy in place to keep exterior sockets powered off is something you need to do now to discourage the thieves. Adding keyed access for authorized users e.g. gardening contractors is a possibility. A sign stating that electricity thieves will be towed is another solution. If you're charging without an authorized placard on the dashboard...away you go.