I had to add this -- once again, understanding the meaning of "competencies" helps when determining how many are enough --

This is from:http://www.nwlink.com/~donclark/hrd/case/compet1.html

Competencies are probably most closely related to abilities. However, in our craft, the term ability normally means either able to do or a special talent; while competencies relate more to expertise and experience. Competencies can be thought of as the state or quality of being well qualified to perform a task. A person gains competency through education, training, experience, or natural abilities. Klemp (1980, p21) defined competence as “an underlying characteristic of a person which results in effective and/or superior performance on the job.” While a more detailed definition is “a cluster or related knowledge, skills, and attitudes that reflects a major portion of one's job (a role or responsibility), that correlates with performance on the job, that can be measured with well-accepted standards, and that can be improved with training and and development (Parry, 1996, p50).“

While there are many definitions of competency, most of them have two common elements:

The competency is an observable and measurable knowledge and skills.
The knowledge and skills must distinguish between superior performers (or exemplary performance) and other performers.