When experiencing personas for the first time, a common question is, ‘How can three to seven persona descriptions encompass the requirements of an entire user community?’ Traditional user-centered design involved researching the needs of as many users as possible and collecting all of their expressed needs and desires into a long list of requirements. Such an approach makes it difficult to prioritize and typically translates into products that tried to serve all users but ended up serving no user particularly well.

On the spectrum of treating your customer base as a homogeneous community and seeing each and every customer as a unique individual with unique requirements, personas strike an effective balance. They allow you to identify discrete sets of users and create archetypal users that represent distinct groups. Personas and users with similar goals and needs will also be satisfied.

One of the issues commonly encountered is that it is virtually impossible to precisely create requirements in enough detail as to answer all of the thousands and thousands of detailed decisions that occur during the product creation, development, and commercialization process. Instead of trying to specify every single detail of a new offering, it is much more effective for a developer, designer, or marketer to ‘internalize’ an archetypal customer and therefore be able to make effective detailed decisions in the proper context and frame of mind.

More on this topic can be found in "An introduction to personas and how to create them" from Step Two Designs Pty. Ltd.