Funnily enough we had this conversation at work a couple of days ago. The main thing we could not agree on was do you make it compulsory for everyone and if you don't how do you decide who does it? Personally i don't think it would work.
HB - bad news that three guys could be so rude, but at the end of last year i got physically assaulted by a 17/18yr old girl chav with a wine bottle and i ended up with a cracking black eye and a huge selling on the side of my head. My brain could not compute what had happened so i legged it (and tripped over a kerb whilst making my stylish exit!!).