working at home? Who cares

Working at home is kind of trendy these days. But who knows what people are doing at home. I think it is necessary to have certain rules restricting how many days people can work at home each month. I can think of plenty advantages of working at home for the employees, such as

saving petrol bills
taking care of kids
doing second job
slip out for a while
having a snap
...

but hardly I can find any advantages for employer and other colleagues.

Since it is trendy now, one of my colleagues actually work at home 3 days a week. Some old fashioned guys do make gossips. But who cares...