I avoid the interstates here, but hit I95 probably twice a week. The limit is posted 70mph here, and I probably set my cruise control at 74...aside from the bus-size RVs I'm probably one of the slower ones on the road.
Drive-offs? They've had to park "ghost cars" (unoccupied police vehicles) at various gas stations to discourage the idea, but that's been going on for at least 10 years.
Siphoning or stealing fuel? I've heard of some stations getting hit, but not cars. In Orlando they just caught some people that disabled part of a fuel pump so they could use the pump without anyone knowing.
Over the past couple of years I've heard of other cases where people would park trailers over the main fuel tank, then they'd open a hatch in the floor and pump fuel into a holding tank in the back of the trailer, close everything up, then drive off.