People expect to be safe on holiday because it is a relatively innocent activity (except in environmental terms). Cosseted by tour operators and ensconced in modern hotels, tourists take so much of their familiar life with them that risks seem unreal. This perception is reinforced by a residual belief that guests should be a protected species, which they often are for financial rather than traditional reasons. The income they generate is so important to many countries that they are given privileges and protection denied to local people.
One look at the travel advisory notices put out by the Foreign Office and the US State Department presents a darker picture, however. The opening and closing of different parts of the world to tourism, and the warnings attached to many parts that remain open, reveal greater dangers than the brochures suggest. The threats are not confined to poorer countries. Parts of the US can be as risky to visit as southern Egypt. Tourists are tempting targets everywhere because they usually carry more money and valuables than locals.
In Egypt, however, they have also become a target for terrorists because of their importance to the national economy. Killing them hits the government where it hurts most - in its balance of payments. In Algeria, too, foreign nationals have been targeted by Muslim fundamentalists with similar hopes of destabilising the government.
If the habit spreads of attacking foreign visitors for political reasons, the tourist map of the world could change more sharply. The prospect of being killed for being foreign will feel more threatening than that of being robbed for one's wallet or handbag.
As one area closes, however, others open. Beirut, Albania and Cuba, for instance, are now reaching out for tourists. A multinational industry that generates dollars 3,400bn a year will always attract new investors, find new outlets and encourage governments to protect its customers. Human curiosity about the way other people live will continue to provide the demand for its services. That curiosity can be a glue that helps bind humanity - a much-needed glue, since the varying levels of risk provide a disturbing map of the many social and political fissures around the globe.