I was at a party last night and a neighbor who works for a commercial HVAC company explained his method of ripping off the gas company.
He says that gas is a commodity and therefore is typically cheaper in the summer than in the winter. In the summer he "over-reads" his meter by 35 - 40 therms on average, paying for the extra therms at the cheaper price.
In the winter, he "under-reads" his meter by the same amount, paying for fewer of the expensive therms.
Since he is sending in his card every month, and he is staying within "average use" for a homeowner, they only come to read his meter once a year and it's always near the end of winter when his over-reads and under-reads have just about cancelled out.
As they ask on Mythbusters - Busted, Confirmed or Plausible?