The preliminary results of a 2008 survey of public history professionals was recently released. These results are available via the American Historical Association publication Perspectives on History and in the NCPH newsletter.
This survey was organized in an attempt to provide better understanding of the public history profession, and perhaps create a clearer definition of public history. Almost 4,000 persons were surveyed, in an attempt to gain an understanding of "who is drawn to this area of employment, and what their concerns were."
The results of the survey, reflect the current vagueness of the public history field. Many of those surveyed did not define themselves as public historians, even though they may be involved in history outside of academia. Similarly, some historians working in academia defined themselves as public historians based on what they teach and research.
Can one be a public historian while working in academia? I would say yes, however it is not a common occurrence. There are some professors who write for a larger audience and aim to engage people outside of the ivory tower, however these persons are not the current norm.
Additionally, the most common field associated with public history is currently museum based work. Museums are definitely within the realm of public history. However there are many more ways in which historical work can be turned into public history. One of the great benefits of practicing public history is the diversity of the field, it is not limited to museums. Greater awareness of the different types of public history needs to be created.
 "Preliminary Results from the 2008 Survey of Public History Professionals." Perspectives on History, September 2009, http://www.historians.org/perspectives/issues/2009/0909/0909pub1.cfm