I think thieves fall into 2 groups, the first is so dumb that they wouldn't be able to read this website and the second already knows how to steal fuel.
There are now lots of news items on fuel theft. Today I saw one on a service station that has installed tyre spikes and last week another item on a car parked near a rail commuter station that had been siphoned twice.
2 weeks ago i filled my daughters car and had to pre pay, the first (but undoubtedly the last) time that I had experienced this. This was 3pm in western Sydney.
About 15 years ago in rural NSW a farmer accosted a thief stealing fuel from his tank one night. He fired a warning shot into the car that the thief was filling. Unfortunatly the thief's girlfriend was hiding in the car and was wounded. The farmer was charged and sued for injuries and basically ruined. I expect more such violence (from both thieves, victims and frustrated motorists) as the fuel supply and economy turn bad.