Thank God it did not happen to me, but recently someone got an e-mail they wrote forwarded to a whole bunch of other people. This has happened to me, but for the most part I am careful about what I write in e-mail or who I send it to. In the professional world it can happen quite often. You send an e-mail to someone and all of a sudden everyone in the company has it, or worse you accidently hit a mailing list instead of a single recipient.
Take this as a PSA, be careful about what you write when you e-mail, you never know where it will some day end up.