By Paul Carsten BEIJING (Reuters) – The ascendancy of mobile messaging in China slashed the number of microblog users by 9 percent last year, a government report showed, triggering the steepest decline in the share price of top microblog operator Sina Corp in three months. Blockbuster mobile messaging apps such as Tencent Holdings Ltd’s WeChat have become venues of choice for users who want to express views without fear of retribution. The government threatened legal action against people whose perceived rumors on microblogs such as Sina Weibo are reposted more than 500 times or seen by more than 5,000 people. The number of microblog users fell to 280.8 million from 308.6 million a year earlier, according to the official China Internet Network Information Center report released on Thursday.