Wow this is a big story, how often do you hear about the US Government being sued by a corporation. Well Google seems to think that it is necessary to prove their point.
Google is suing the Government because they believe that they did not fully evaluate Google Apps when choosing a new web-based document system. The Government had stated that it need the system to be a part of Microsoft's Business Productivity Suite. Now since Google isn't Microsoft, they really did not stand a chance in hell.