Hah! NYTimes piece about Mail Goggles — a new service available only to Gmail users,

The experimental program requires any user who enables the function to perform five simple math problems in 60 seconds before sending e-mails between 10 p.m. and 4 a.m. on weekends. That time frame apparently corresponds to the gap between cocktail No. 1 and cocktail No. 4, when tapping out an e-mail message to an ex or a co-worker can seem like the equivalent of bungee jumping without a cord.