I awoke to a flurry of emails from Facebook users in various parts of China, saying that they were unable to access the site for six hours yesterday evening.

Speculation is running high that the cause was censorship, rather than a technical problem, although the evidence is unclear at this time. One big reason for such speculation is that other sites in China that rely on user-created data have been censored. Most strikingly, the third largest video-sharing site in China, 56.com, has been down for nearly a month, due to what is almost certainly censorship.

A quick look shows Twitter users in China and Chinese blogs covering the problem. Ogilvy strategist Kaiser Kuo, George Godula at web2asia, and others have mentioned the downtime — apparently, Facebook was inaccessible from Shanghai, Guangzhou and other major cities. See Summize for more Twitter discussion.

IfGoGo, an English-language blog run by some Chinese developers I met last month, has screenshots of the error message they were seeing.

Inside of China:


Outside of China:


However, another China tech blog, Tech Blog 86, reports it hasn’t seen any downtime.

Most recently, Twitter reports say affected users were subscribers to China Telecom, not China Mobile users and others. While the site is apparently back online everywhere, some China Telecom users are saying the site is running slower now than before it went down.

It’s not clear if the downtime was a technical issue stemming from something like the company moving to local servers. Besides 56.com’s downtime, its rivals Tudou and Youku have both experienced “technical” problems that were also possibly censorship — so I still have to wonder what’s happening with Facebook.

The possible implications of Facebook’s China downtime

Facebook recently introduced a Chinese-language version, to take advantage of what is at least anecdotal reports of its growth in the country and around Asia. Friendster, as I’ve written, is currently the largest social network in Asia, with 36 million visitors in April, twice the size of its nearest rival — Facebook. It’s not clear if either company has shown much success so far in China, especially as local incumbents like tencent.com and others have already gotten big.

Still, Facebook is perhaps the most potent social network among its peers, as it has convinced many of its users to share their real information on the site. Rivals like MySpace and Friendster have tended to be more entertainment-focused. One source in the Chinese internet scene has told me the government views Facebook more seriously because of this, as its users may be inclined to share things the government actively censors, like pornography and hard-hitting criticism.

The company has recently draw some extra attention from the Chinese government, too. Premier Wan Jiabao’s Facebook fan page has seen tens of thousands of ethnic Chinese and other people from around the world express their support for the his governments’ fast-moving efforts to help victims of a terrible earthquake in the country last month. At the time, a government official responded to the Facebook page by thanking all of the supporters. Hopefully, his page — which appears to have been created by a fan and not the government — shows the government how it can benefit from social networks like Facebook.

It’s also worth noting that Facebook has been rumored elsewhere to have recently hired someone who is no doubt well-versed in the operations of the Chinese media censors, recently hiring Yang Xiaoyan, a brand director, away from the government-run China Central Television.

China now has more 230 million internet users — more than the US — and given the fast pace that the country’s other billion people are getting internet access, it will no doubt continue to be one of the largest markets in the world. Facebook can’t afford to miss out on it, especially as rivals like Friendster move in. We’ll be following this story closely.