There are Freudian slips — and, as an old pal once referred to them — Freudian sends, emails whose bitchy, gossipy content accidentally gets sent to the object of your bitching.
I've never done this myself (it's only a matter of time), but I keep hearing stories about people who have. The awkwardness of having to face that person and apologize, probably only to deal with their eternal wrath, is hard to imagine. Have you ever "accidentally" sent someone a message talking stink about them, or knew someone who did? What was the fallout?