What could account for the poor performance? The Golden Shield Project for one, which (among other things) prevents the sale of iPhones with Wi-Fi enabled. iPhones purchased outside of China do have Wi-Fi, of course. Another factor could be China's bustling black market. Despite the recent official release, the iPhone has been available in China for quite some time now. AppleInsider estimates that nearly 2 million iPhones are already circulating China, most of them jailbroken.
Cost is another factor. For example, a contract-free 32GB iPhone 3GS costs 6,999 yuan (approximately US$1,024 as of this writing) in China, compared to about US$800 in Hong Kong.
The news isn't all gloom-and-doom, however. AppleInsider reports that those who do purchase iPhones legitimately are flocking to the App Store. Still, the problem of getting more official iPhones into the hands of Chinese customers remains.
*As of Dec. 3rd, 2009.