Social sharing is a vital part of online community building--whether be it a simple trade forum or a complex social network. Social sharing can help build traffic for a website and further marketing performance goals. For a user, finding valuable and intrinsicly interesting content can be helpful, fun and is at the heart of what the web is about.
It is important to remember that not all content you and your brand shares in a social community should be self-promotional in nature. Remember to be a participant in the community. People join social communities for a range of reasons, but least of these reasons is to be marketed to by brands. Ultimately, by overly "selling" your brand through social websites, you run the risk of driving potential allies, users and customers away. Instead, practice sharing great content that is truly useful.