This is the Clooneys' business but personally I wouldn't do that, any more than I would place a basket by the door with slippers in for people to remove their shoes. I partly understand the need to be the king of one's castle but well socialised people don't need that degree of policing. The next question is whether you actually let strangers into your home. Of course we all do - I think - tradespeople - can we really relieve them of their phones? However, I did once ask a cleaner to turn her phone off as she was always whispering. She refused, saying she had to be available if there were a phone call about her children from school.