Since the success of social media in private usage settings, social media applications spread rapidly in the working context. In business internal contexts these applications seem useful as a measure for strategic knowledge management. Social media in this context promises to offer adequate facilities to support a systematic storage of knowledge as well as a support of knowledge exchange and communication in enterprises. But since social media is only successful when used, the usage motivation of employees is one central key for their success. Therefore this paper focusses on the motivation to use social media professionally. To achieve this we are investigating the influence of user diversity factors such as age, gender, and social media expertise on aspects of usage motivation. In a study with N=84 the employees of an enterprise were asked which reasons for using social media are relevant to them. Findings show that both factors age and gender reveal a relatively low influence on the factors evaluation of usage motives, tools (as a measure for motivation), and incentives/reinforcements for social network usage. In contrast both expertise with social media and achievement motivation revealed many correlations with both usage motives and tools as well as incentives and reinforcements.