From Strategy Page:
Next year, China hosts the Olympics, and it fears reformers, and dissidents of all sorts, will use the huge influx of foreigners as an opportunity to stage anti-government demonstrations…The government considers it essential for Chinese prestige, as a "major power", that the Olympics go off without a hitch. To that end, the government will round up all known troublemakers and dissidents and put them in preventive detention for the duration of the Olympics. [emphasis added]