What a shocking and terrible story. You're right, people can get lulled into a false sense of security on the Internet.

Another way to keep your privacy safe and those of your friends is, if you are sending out a mass email to people (i.e. forwarding jokes or something), use the BCC: (blind carbon copy) rather than TO: or CC: for everyone. With BCC:, people can't see the other recipients, whereas with the TO: and CC:, they can. After a joke has been forwarded a few times, you don't know who can see your email address, as the "forwards" have accumulated.

Also, when forwarding emails (like jokes, etc., anything that has been forwarded multiple times), delete all those preceding Fwd: Fwd: Fwd: headers that have accumulated.
You never know who could see your name and email address.