I’m with Victoria on this. It’s partly confidence, not feeling part of the group, partly not feeling that I have anything of substance to add to the discussions. And sometimes it’s because the topic is in my expert field and I don’t want to come over all “Well, actually …” without having my credentials clearly on display. After all, I have no idea about the expertise of other respondents in online discussions, and they don’t know mine. It makes discussions ‘interesting’ at times. Once I’m wholly comfortable with a forum, I do tend to talk too much though.