As I observed some of the famous Web sites in China, there are a tendency of using number in their domain names. Some notable sites in China, e.g. China’s first search engine, i.e. 3721.com; a famous China social networking site, i.e. 51.com, and my favorite sites in China that are hao123.net or 163.com, they all have number in their domain names.

I wonder this is due to the cultural or language (pronoun) localization? Or do these site owners tend to believe using numbering technique in their sites, their sites would get a better ranking in China’s search engine such as Baidu.com or Qihoo.com?