Major events such as World's Fairs and the Olympics always provide an excuse for governments to "clean things up" in the host cities before the guests arrive. Police sweep people the leaders consider undesirable, embarrassing or just plain unsightly out of public view. The victims vary with the time and place: the poor, the homeless, unpopular minority groups, drug addicts and gay people have all been among them. The list always includes sex workers; even in countries where prostitution is legal the moralists feel compelled to purge the most visible manifestations of the sex trade from areas where visitors might encounter them. Xenophobia is also heightened by such events, as those so predisposed fear the prospect of strangers coming to town, bringing with them outlandish and alien forms of sin and crime. Together, writes Maggie McNeill, these two factors may be the origin of one of the stranger (yet more persistent) myths of our time: the idea that some Lost Tribe of Gypsy Harlots wanders about the world from mega-event to mega-event, unimpeded by the usual logistics of transport and lodging which should make the migration of such a large group a daunting task indeed.