Understanding the generational stereotypes is an important part of any manager's job. But where a significant number of managers fail is taking the stereotypes for gospel. And instead of treating each employee as an individual who may or may not fit the stereotype, the assumption is made that the they will fit the the stereotype.
Another related issue is even within the generational stereotypes there are different ways to motivate individuals depending on the background of the individual. An example would be that most risk-takers are somewhat motivated by money but a risk-taker who has all the creature comforts and is working for other than financial reasons, a cash award means absolutely nothing to that individual.