When I would bring stuff to the dump, I would see people pick up all the metal items from the pile after they dump their trash. It would add weight to their car, so they were charged less, and then they could recycle the metals for even more money. I found it to be a brilliant system. Not entirely sure if it's fraud or not...

Theft followed by fraud I think. Edit: or maybe the fraud occurs at the weigh scales and the theft occurs at the exit gate? IANAL

I wonder how often people overdo this, and face some awkward questions when their weight is higher on the way out.