I am thinking of a company* that sold customizable software to large customers who demanded the ability to customize. It also sold new features, which would have to be created by the development staff. At one point, the sales and development staff wound up in different cities, to the technical people weren't able to sit on the overenthusiastic sales people.
The sales people found that they could sell new features, and (a) it made it easier to close the sale, and (b) custom development cost money, so it raised the dollar amount of the sale. Therefore, by overselling custom features, a salescritter could increase not only the probability of a big commission but the size of the commission. The development staff had different ideas about getting flooded by requests for custom features, in that it destroyed the ability to move the main product forward in any coherent fashion, and resulted in large delays in actually shipping and (this was important) getting paid. This continued until top management stepped in and did something that actually made sense in the situation (imagine my surprise).
Smart people will know how to game the reward system, no matter in what field.
*I would like** to formally announce that this is not a company I worked at and signed an agreement not to talk about.
**For reasons I'm not discussing here.