But role-based navigation like this poses the same problems it does on other university sites. Users don’t necessarily self-identify, and they often don’t understand which audience category contains the content that they want. For example, many parents view the page for prospective students well before they view the page for parents. Evaluate whether topic-based organization might be more efficient for your users. And if you are using audience-based organization, be sure that each audience is specific and distinct, and include the information that is most relevant to that audience.
Katie Sherwin in: http://www.nngroup.com/articles/breaking-web-conventions/