Your message has been sent. Undo?

Google is launching a GMail Labs feature called "Undo Send," that lets you abort the sending of any GMail message–if you use it within five seconds.

I’m enabling this on my account right now (under the assumption that Google looks at how many people adopt any given Labs feature and uses that information somehow).

This is genius UI design: functionally, it’s exactly the same as having a dialog pop-up to ask “Do you really want to send this message?” and auto-accept after a few seconds. But, as far as the user’s perception is concerned, it’s the polar opposite: instead of being an obnoxious Clippy the Paperclip, you just execute the action like the good computer that you are, but leave a small window of opportunity for the user to scream “Oh shit I didn’t mean to!” and undo.

Not sure who invented this first and I don’t care (I feel like I’ve seen something like this before); all I know is that every single developer in the world needs to look at this very tiny bit of functionality and rethink their worldview around it.

P.S. Forgot to mention: of course, it doesn’t belong in Labs.