I guess Google realized they can't possibly create the whole World in 3D by themselves. Therefore Google released a free 3D modeling software - Google SketchUp. It is a very easy-to-learn 3D modeling application where one can use to create 3D models of architectures in few minutes! You can use this tool for any 3D modeling projects. But what Google really wants you to do is to create realistic 3D models that mirrors the physical architectures in the real world and then upload them to Google Earth. This way, 3D lovers will create a 3D earth for them for free! Great deal eh? What's worth to mention is that there are only two types of files you can export to, 2D graphic (jpg, tif, bmp, png) or Google Earth (kmz). This means it's unlikely you can export your 3D models for other programs such as Blender, 3D Max, Maya or Secondlife.