Google has indicated it may cease to operate in China following a cyber attack aimed at gathering information on human rights activists.
If Google quits China, then it leaves MS yahoo and Baidu as the primary sources for accessing the Chinese searching audience. Without Google, assuming Yahoo and Bing remain, that 30% share will re-distribute. Most likely to Baidu, which will further cement its leadership position, and the remainder may not split equally among Bing and Yahoo users, which would further upset the balance of power for one or the other, and means growing in the Chinese market is likely to make it very difficult for at least one of them. For advertisers looking to target the Chinese market, it means a greater dependency on foreign operators who are less familiar to them, and less integrated with their ad operations.
For the US and global advertising industry it means ad dollars are going to go overseas into Chinese pockets as opposed to strengthening the US coffers too.