Cool hack and awesome, fun writing, but on a more serious note : how is knowing your friends' usage/sleep patterns useful in any way? Could it be used for some

Cool hack and awesome, fun writing, but on a more serious note : how is knowing your friends' usage/sleep patterns useful in any way? Could it be used for some dark, machiavélique purpose? And how about for advertisers? "Get your sleeping pills here" type ads?