I am fascinated by this Google Labs "Undo Send Mail" feature. So, how does it exactly work? You click "Send", the recipient receives it, she reads it, gets mad at you. Later you realize you shouldn't have sent it, you hit "Undo Send Mail", then a man in a black suit working for Google sneaks in the recipient's home, hacks her e-mail account and deletes the post, also from her computer if necessary, then flashes a bright light in front of her, while saying "You never received that e-mail. It was a meteorological balloon". How clever! I wonder how I could have agreed for a second with the post, thinking that sending e-mails cannot be undone!