This grounded theory study responds to the 21^st Century dilemma medical schools encounter as online social networking sites like Facebook reveal more and more about their students—do professionally incongruous online behaviors indicate a lack of essential traits required to be a physician? By contextually situating the inquiry at one medical school over a period of three years, findings revealed the main concerns students had regarding professionalism as it relates to Facebook and detailed strategies employed to resolve those concerns as a substantive theory of digital identity dissonance. Participants revealed an awareness of desired behaviors espoused by professionalism expectations, but discovery of a looped pattern of telling demonstrated a reactive reasoning process seemingly incompatible with institutional norms but indicative of identity acquisition tension. Theoretical conceptualization of the data expanded Bourdieu's notion of habitus to a novel concept of Facebook Native Habitus (FBNH). Identity guarding emerged in analysis as a basic social process characterized by a reactive reasoning process through which enculturated members of a group negotiate thoughts and feelings perceived to be incongruent with in-group expectations. Identity guarding is a subconscious strategy used in managing presentation of self and is the formal theory developed in this study.