A one plant-one pollinator relationship provides high fidelity, meaning that any reward provided by the plant to the pollinator will not be wasted by the pollen going to the wrong flower. On the other hand, the plant becomes highly dependent on the pollinator--any drop in the pollinator's population spells great trouble for the plant.
Work Step by Step
Look at the chapter from the point-of-view of the plant: it provides a reward to pollinators and wants a result (pollination) in return. How could this be useful or a problem. You could think of an analogy: farm stands which operate on the honor system. Someone puts out produce by the road and expects that the requested price be put in a can. There is a reward (the produce), and a result (payment) is expected. This system works for the farmer, who doesn't have to pay wages to man the stand, if the customer is honest and pays. If not, the farmer loses. The farmer is like the flowering plant, and the customer is like the pollinator.