Gates and co have admitted that a weakness in Internet Explorer allowed the Chinese government (allegedly) to attack the Gmail accounts of human rights activists, prompting Google to leave the country. And potentially causing a diplomatic incident.
Microsoft director of security Mike Reavey said the following in a blog post, according to the BBC:
Based upon our investigations, we have determined that Internet Explorer was one of the vectors used in targeted and sophisticated attacks against Google and possibly other corporate networks.
In short: if you're going to fight oppression in China, use a Mac.