The prevalence of social media use has significantly expanded the landscape of marketing communication and brand community management. Currently, various international brand players are beginning to develop ways of communicating with their customers on social media. This study focuses on the marketing applications of social media by examining the key motivations influencing the disclosure of personal information and participation in commercial activities of Facebook users in Hong Kong. The 566 responses were analyzed using descriptive statistics, reliability analysis and structural equation modeling. The results support most of our hypotheses, suggesting that perceived convenience of maintaining relationships, enjoyment of activities, self-presentation, social presence, and perceived risks of privacy invasion have significant impacts on users' self-disclosure on Facebook and participation in commercial activities. The findings contribute to the literature on internet consumer behavior and have implications for the use of social media tools in marketing.