Wow. There is a lot of misconception here, but also a lot of good points.
I worked at a gas station for 4 months. Plenty long enough to get to know things like this. Of course all of the information with regards to these statistics depends on the size of the gas station or which corporation it is.
That being said, from what I know.
1. Some states force pre-pay. When drive-off's usually get particularly bad in a certain area, most companies will switch to pre-pay only.
2. For states that don't force pre-pay of some sort, most state that they you will loose your liscencse:
This is not exactly true. Most (at least corporate) gas stations will not report you, period. The one that I worked for is this way.
If you drive off after pumping a tank of gas, we would record the loss and move on. We would NOT approach you about it, not chase you down, and not call the police (unless, perhaps, you had done it multiple times at one location).
Consider the scenario: Two people pull up to two different pumps (seperated by perhaps 2 or 3 minutes) and start pumping gas. One person drives off and we call the police (as if they really care). Then, the second person comes into the store and says "Hey - i'll pay for me and my wife."
Instant lawsuit.
3. Many (perhaps even most) gas stations do not make money off of gas (due to a number of reasons, including gas). They make money off of what they sell inside the store, though - which is why pre-pay isn't nationwide. Pre-pay discourages people buying things other than gas because of the longer waits. Either way, gas isn't that profitable for the station.
4. Most corporations get stipends for a certain amount of drive-offs (it's an assumed cost of running a gas station). The place I worked at has measures to reduce drive off.