I've built map applications while based in Beijing. Google is definitely skewed here, by decree of the Chinese government. The interesting thing is that the skew is different for various regions in China, but it hasn't changed for years. If you correct for the offset in Beijing, everything will be fine as it is the same across the whole city. You can create a map of offsets for the major cities and be done with it.
They claim that the offset is for security purposes but this simple fix shows that the excuse is bullshit. In reality the Chinese put all kinds of barriers to entry for foreign companies to make it difficult to penetrate the market. Another example is that you have to dual home your servers to both china unicom and china Telecom, as the traffic between the two networks is degraded on purpose. You thus have to purchase a special DNS service that differentiates between requests on the two networks.
In the same vein, the purpose of the great firewall is more economic than political, being a highly successful form of protectionism.
Why don't non-china mapping companies have a table of these offsets and simply apply them everywhere (well, maybe except chinese IP adresses) ?
It seems a tiny amount of work compared to, say, gathering the actual street data itself; and it would be an useful thing to make this data available to the public like openstreetmap data.
