One of the ways we make this site safer for you is by having everyone register for membership to participate in the groups. What it means, though, is that we have to get everyone's email address. Your email address doesn't show up on the site, though, and we don't share it with anyone anywhere else either. We do use it ourselves sometimes, to send you messages, like what's new on the site, or if there's something important you need to know about.
Your username is what gets shown on the site, but it doesn't have to be a real name, so it doesn't need to let anyone know who you really are.
We keep all your account information in a database on the server. No one can guarantee 100% security on any computer system, including servers, but we've done what we can to keep the database from being hacked.