Small tremors sometimes foreshadow bigger shocks. Few people will have known before this week that Steven Spielberg – he of Jaws, Jurassic Park, E.T. and other Hollywood epics – was to lend his creative talents to the Beijing Olympics. Of itself, his withdrawal on grounds of conscience scarcely registers on the Richter scale. Mr Spielberg’s protest, though, is not without significance. It maps out uncomfortable terrain for China that reaches well beyond the choreography of this summer’s Olympic ceremonies.