Microsoft seems to be working many different angles to wipe out any advantage that Google should get as the primary developer of the Android OS for Smartphones. The sneaky angle is to persuade the Smartphone makers to replace Google as the default search engine with Microsoft's own Bing search engine. For example, the LG Revolution has the Android OS, however as the PC Mag review says, it has been thoroughly Binged. Bing is the default search engine and Bing Maps is the default mapping application. My son, who recently got a LG Revolution told me that he had to download Google Maps to get the mapping application he prefers.
Microsoft has also been going after the various Android smartphone makers, getting them to pay royalties on Microsoft patents. Reputedly, HTC is paying Microsoft $15 per smartphone to license patents. It would not surprise me if Microsoft is making more money from licensing patents to Android handset makers than it is making from selling its own Windows 7 Mobile operating system to handset makers. They are certainly making more profit from Android than from Windows 7.
Microsoft could apply pressure other smartphone makers to set the default search engine to Bing in exchange for reduced payments of royalties. If this becomes widespread, Google loses the advantage that it gets from having developed Android, and in the long run even threatens the existence of Android. If Google gets no advantage from developing Android why should it continue? This is only a tiny slice of what is going on with mobile patents, however the ball seems to be in Google's court and we are waiting to see what they do with it.