all it took was a single tweet to send the Chinese government into panic last Sunday. The tweet, originating in the US, publicised a call posted on the US-based website Boxun for Chinese citizens to assemble in cities across the country to start a jasmine revolution, inspired by events in the Middle East.  The tweet did not produce nationwide protest but it certainly had an impact, despite the fact that Twitter is blocked in China. Saturday saw the first wave of arrests of human rights activists, lawyers and other citizens known to disagree with the regime. The detentions continued on Sunday morning until the list of names passed 100. On Sunday afternoon, outside the McDonald's on Wangfujing, one of Beijing's biggest shopping streets, police both uniformed and plainclothed, outnumbered the curious, the passersby, the shoppers and even, no doubt, some potential protesters.  Online, explosive words like "tomorrow", "today" and "jasmine" fell under prohibition. The Boxun website was targeted with a severe distributed denial of service (DDoS) attack, and users of social media in China found themselves unable to post photographs, forward posts or search. There was no revolution last Sunday, but as an exercise in tweaking the tiger's tale it was hard to beat.  Now, the anonymous organisers of last Sunday's "citizens' stroll" have called for it to be repeated every Sunday at 2pm. The question is not so much how many people will show up to protest at the usual list of grievances - corruption, lack of accountability, abuse of the law, arbitrary use of power - but the fraying of sensitive official nerves each week as the authorities wonder if this might be the day it does take off.  It would be unwise to exaggerate the parallels between discontent in the Middle East and in China. Certainly discontent in China exists, but for many people the last two decades have brought rising living standards and a sense of personal freedom. Given that, it is not easy to explain the evident fears of the regime. according to a study last year by Beijing's Qinghua University, the government now spends more on internal security than it does on external defence. If those figures are accurate, it offers an interesting snapshot of where the regime thinks its most dangerous enemies are.  Images of successful nonviolent protest, then, are deeply unwelcome, because they recall similar images of Tiananmen Square in 1989 and serve as a reminder for the discontented that change is possible, and that there is unfinished political business to attend to.  The suggestion that the examples of Tunisia or Egypt have anything to say to China brings on the government's jitters, but while the regime can clamp down on the news periodically, it can no longer keep the outside world at bay. China admits to 30,000 Chinese citizens in Libya, for instance