More interesting than I thought:
BBC - Travel - Why China is obsessed with numbers
Not everyone in China has perfect grasp of pinyin. If websites have pinyin names, it might actually be difficult for some people to figure out which letters to write,For instance, 163.com is the website address of Chinese internet company NetEase. Its a throwback to the days of dial-up, when customers had to enter 163 to go online. The phone companies China Telecom and China Unicom simply re-appropriated their well-known customer service numbers as domain names, 10086.cn and 10010.cn, respectively.Among e-commerce conglomerate Alibabas various platforms is 1688.com, with the numbers pronounced ee-lio-ba-ba in Mandarin.You can order your McMuffin online by typing 4008-517-517.cn because 517 in Mandarin is wu yi qi. Almost like wo yao chuh or I want to eat (chuh is the closest phonetic spelling for chi, the actual word for eat).