BEIJING -- China's Twitter was raucous Thursday with horn-tooting over Beijing's gold rush at the London Olympics, a digital reflection of the nation's exuberant mood – embellished with flashing emoticons. Earlier passions have been ignited on the site by a deadly high speed rail crash and outrage over factory pollution.Launched in 2009, China's leading microblog site, Sina Weibo, has given a digital megaphone to more than 300 million Chinese, prompting many to wonder if it might drive Arab Spring-style political change and democratic reforms.