Recent research evidence suggests that while extraversion is predictive of many positive social outcomes, it may not be extraversion itself that matters. Instead, it may be possession of social skills or competencies that are better predictors of social outcomes than personality constructs such as extraversion. Let me explain.
Extraversion is a core personality trait that is associated with high levels of energy, expressing emotions, and seeking the company of others. Extraverts seek out social situations. Intraverts are more low-key, deliberate, and often seek solitude. There is a great deal of research that shows that extraverts are evaluated more positively in initial encounters (usually in social situations, and likely because they get "noticed"). Extraverts are also evaluated more positively in job interviews and, most relevant to my area of study -- leadership, extraverts are more likely to attain leadership positions and to be seen as more effective leaders. So, there is a seeming advantage to being an extravert.