When you are sending emails of, oh, I don't know, the latest lol cat picture from icanhascheezburger.com to multiple people, especially to those that may not know each other, you really should you BCC to protect everyone's privacy. bccplease.com is a site that tells you how to do it, and you can also send this site to those that do not BCC your address when they send out that "Obama is a radical muslim" email.