Somebody at Google must have had a bad habit of drinking a little too much and using his/her computer for communication purposes following. Looks like they used their 20% rule to create a way to curb their drunk
Gmail labs: Stop sending mail you later regret
Enabling the feature in your Gmail requires you to answer a series math problems in a certain amount of time to be able to send the email between the hours of 10p and 4a on Friday and Saturday nights.
Now, if only we could get this system into every car on the road.