I used to work in a bar and got on with the bouncers really well and asked them about the whole pickin on people thing and they agreed with it. They said they get bored and do it for a laugh. It might be someone's hair, shoes, jeans or socks but they would just refuse the guy and use the age old "we don't have to give a reason, you're just not getting in tonight.maybe nother night though". So yes, it does happen. Not everyone does it but some do. I guess it passes the time...