Twitter, Foursquare, Angry Birds are very well known and strongly downloaded in the world.
Many brands are investing on applications to get closer to fans.
Facebook is the main social network now. MySpace is declining strongly. Google Wave is a failure. Rumors say that it will be replaced by a new social service.
Tencent and Baidu are still growing. Tencent offers mobile applications to users that are convenient.
Both Baidu and Tencent should redefine their respective strategies to offer services becoming more and more smartphone friendly. The experience has to be easy, fast, and fun!