Most Internet users belong to an online community to share ideas and information with people who enjoy similar interests. Such communities include e-mail distribution lists, blogging sites, message boards, newsgroups, and more. But the friendly nature of these communities can also present a risk to your personal information. You can help protect your privacy and still enjoy the benefits of these groups by following a few basic rules, both in your online habits and in choosing the communities themselves.
Source: http://www.microsoft.com/athome/security/online/community_safety.mspx