I'm old enough to remember the rash of siphoning during the first fuel crisis. I see history repeating itself, but this time with extension cords.
I installed switches on all my exterior outlets after I found out that a former neighbor was plugging his pool filter into one of them after I left for work.
I shop at Fry's in San Diego fairly frequently. There is a large concrete area in front of the store where all the motorcyclists park. My usual spot. There is an electric outlet on the outside of the building accessible to that area. Last Summer, the bike parking area had an unexpected intruder. A Nissan Leaf was pulled up to the building and stealing electricity while the owner shopped inside for a few hours. It was very discharged. He was trapped until there was enough power to go. I'm sure his wife spent a lot more money inside while waiting than he saved with stolen electricity vs gasoline.