China's virtual landscape

Sina (SINA) offers users a suite of services that includes email, a one-stop shop for user-generated book reviews, a news site and social network.

The company's main services are found on Sina.com, the 15th most popular Internet site. Sina's portal provides regional content, including news on everything from luxury goods to personal finance.

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But it's better known as the operator of Weibo, China's version of Twitter (TWTR). Weibo boasts 54 million daily active users, far fewer than Twitter's 200 million, but an impressive number nonetheless for a Chinese service that has yet to enter foreign markets in a big way.

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It's the Weibo network that gives Sina an edge: Weibo's ad revenue for the third quarter was up 125% compared to last year. Weibo's pull is so strong that Alibaba recently purchased an 18% stake in the unit for $586 million.

Headquartered in Shanghai, the company is worth around $5.3 billion and its shares have risen 300% since listing in New York in 2000.

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