HONG KONG -- Douglas Zhang describes himself as "a QQ person through and through."

A "VIP" subscriber to QQ, China's most popular instant-messaging service, the 24-year-old Beijing information-technology professional has more than 100 QQ friends in his contacts list and keeps several premium QQ numbers, which each cost him 10 yuan ($1.43) a month. In addition to messaging, he reads the news on QQ.com and participates in discussions in one of the eight QQ chat groups he has joined.

"I...