I think it's about the potential for injury though. There was a case of a woman being blinded due to having an egg thrown at her in the street. So, albeit the chances are slim, it could end pretty badly, as it did for her.If we examine a lot of these milkshake/egg/manure assaults there is no actual injury, rather there is insult, mockery and inconvenience caused to the victims, nothing more than a bruised ego.