As Alibaba celebrates its IPO, US Internet firms suffer from being shut out of China

[Commentary] Overlooked amid the excitement over Alibaba's blockbuster IPO on the New York Stock Exchange was one of the reasons for the company's smashing debut: The Chinese market it dominates is all but blocked for Silicon Valley rivals like Google, Facebook and Twitter.

That's no small thing now, and it will be an increasingly important issue in the future. US Internet companies want to expand in China, but they haven't had much success. Some tech firms, most notably Google, have tussled with the government over censorship. Others have run into antitrust issues or suffered from the weak intellectual property laws in China. All these problems for US companies have allowed firms like Alibaba, as well as Baidu, the Google of China, and Tencent, the social networking firm that owns the popular WeChat messaging service, to establish positions in China as market leaders.