Have you ever promoted someone when you weren't sure if he or she deserved it? Then both of you probably personally experienced how a promotion like this is a waste of time, leading to a loss of morale and an increase in frustration. Of course, this doesn't only affect you, but the whole company.
The problem often lies in the fact that managers promote their subordinates rather randomly, rather than on the basis of strategic thinking. What can you do to prevent yourself from doing this again?