User Population Vs User Expertise

Mapping user expertise against the user population of a product tends to result in a bell shaped curve.  Indicating that most of the user population for a piece of software has an intermediate level of expertise.  This is an important observation when developing software as developers (as expert users themselves) will tend to develop more expert features and customer support will push for more beginner features.  There is then a high probability that the largest part of the user population (the intermediate users) will be ignored, at the cost of increased product adoption or sales.