The Blazer sleeps at the end of the driveway, right at the street, with the filler cap away from my windows. Easy mark for somebody who parks in the Mr. Fixit business lot next door and knows how to siphon.
Losing the fuel is annoying, but I guess I ought to be happy, as one fairly recent local SOP has been to punch a hole in the bottom of the tank and drain it into a large capped pan made for oil changes, letting any excess drain out under the vehicle.
Amazing there haven't been serious fires...yet.