The recent dust-up over working from home or working at work has brought a few issues to the forefront. Primarily, that dealing with a young, mobile and educated workforce is hard. When millennials work for you, life is going to be very different: they are not their father's workforce.
Today's smart workers get paid for thinking -- and there is no "off" switch in our brains. You'll probably never get fired from a smart company for keeping irregular hours if you consistently over-achieve on your objectives, but you might very well lose your job if you're always at work from 9 to 5 and produce very little.