East-West-Connect.com has a great overview of microblogs in China.

"While the English microblog market is characterized as being ‘Twitter and challengers we compare to Twitter,’ the Chinese microblogosphere is bursting with competition, creativity and copying. Multiple contenders jostle with each other for 400 million Chinese Internet users that haven’t yet decided which microblog they would prefer to use, if any.

To add to the confusion, Chinese government censors have already shut down a couple microblogs.

As of February 2010, there are at least 10 microblogs that show promise."

The post then lists a few thoughts on several microblogs. It doesn't actually even touch on SEO, but microblogs are excellent places to spread the word and potentially get quality links back from your  followers' websites and blogs. Sina, especially has potential now because it is easy-to-use and has a large, active, growing userbase.