Yeah, it's only going to get worse I'm afraid. To foil potential gas thieves, I've measured the fuel tank and mounting points on my wifes '99 Villager van. I have a friend who is welding up a 1/4" steel "tub" that will enclose the tank completely from below and also shield the filler neck. I've already added a switch to the fuel cap access door and integrated it into the van's alarm system. Fortunately, the fuel lines are already fairly inaccessable and I'm going to add 1/4" steel plates in a couple of places just in case.
If anyone want so syphon or puncture the tank, or cut and use a fuel line, they are really going to have to work at it.
Now, if I could only get my wife to practice with the Glock...