Checking on Twitter friends sleeping schedule

I suppose it’s easy to find out the sleeping schedule of a twitter user. All you need to do is record all the twitting time and plot a statistic graph. The time frame which there is no twits from the user can be defined as sleeping time. Of cause the person has to be a frequent twitter user who text almost every hour. So the question is why do people find out or need to know a person’s sleeping schedule. I sure don’t know the answer to that question. But I do know a site which can find the sleeping schedule of your twitter friends. Check out SleepingTime.org as you just need to provide twitter username to run the estimation sleeping schedule.