Amid the sad news that former Vice President Al Gore and his wife decided to split, CNN inadvertently published Al Gore's email address when posting an email sent by the former VP and his wife to close friends. After claiming it received the email from a "longtime family friend," the news outlet posted the email in its entirety — including the email address it was sent from. Though it has since been removed, the address was live on the site for nearly two hours; long enough for thousands of people to see.
I once fell victim to a similar disaster — CCing a group of recipients on an invitation instead of BCCing everyone. I received no less than 10 angry emails from contacts upset that their personal addresses were shared with a large group. I've also been on the receiving end of such a gaffe, but clearly never on this scale. Just another one to add to the list of top Internet mistakes of all time, I guess! Has something like this ever happened to you?