Our group was one of the originators of expertise sharing as an area of study. Our work has included expertise finders, people recommenders, and collaborative help systems. As well, we have conducted many studies of how people helped one another through computer-mediated communications and within organizations. As the span of networks and computational systems expanded, the scope of our study expanded to Internet-scale systems and communities. Recent work has also expanded to Q&A communities (question-and-answer) communities and social search.