There’s bad news for Google in China this month as the country’s largest Web portal has stopped using (and thereby promoting) Google’s main product.  Sina will now rely on search technology of its own rather than allow Google’s search engine to serve its users.

A quick nod to glass-half-full types: this development might work in Google’s favor if lots of Sina users notice a decrease in search quality and draw attention to the issue, essentially giving Google free PR.  But that scenario’s something of a long shot.

Otherwise, this just represents the loss of an important partner in China, meaning Google’s revenues in the country may take a hit.

Also, it’s possible Google will become even more of an outcast in China as a result of this change.  Google’s been on a bit of a losing streak, after all, with partners abandoning it left and right after the big censorship brouhaha and the Chinese government (allegedly) blocking Gmail again.

At this rate, it’s hard not to question whether anyone will want to do business with Google in the future, and what sort of business it’ll be allowed to conduct.

Anyway, here’s a more complete look at Google’s performance in China.  Owen Fletcher, who’s based in Beijing, noted, “Google’s share of revenue in China’s online search market extended its slide in the last three months of 2010, falling to 19.6% from 21.6% in the third quarter and from a peak of 35.6% in the last three months of 2009, according to Beijing research firm Analysys International.  Baidu’s market share rose to 75.5% from 73% in the third quarter and compared with 58.4% in the last three months of 2009, according to Analysys.”