it's called competition and in a wild frontier like China with the largest potential market, why not use a backdoor built into your browser (Explorer 6) to undermine your #1 rival? I don't know if you have notice it or not, but Google has been under attack since MS Bing took the stage. There didn't seem to be any problems, or at least they weren't reported, prior to it's introduction.
This issue goes to the argument as to why it was important to build
Chrome.