Yesterday (August 6), Google announced that user generated 3D content for the official 3D Layer of Google Earth will soon (with October 1) be over. With this move, an era of over seven years will be over. Google acquired SketchUp in 2006 and immediately released a free version of the software in order to encourage modellers to populate Google Earth with 3D content. Later Building Maker was also added (this was stopped in June this year) and eventually 45 Degree 3D Imagery was also added - this latter one to finally replace 3D models made in either SketchUp or Building Maker.

Certainly, beside enthusiastic amateurs, lots of small (or big) businesses have been based on modelling for Google Earth but of course, once someone founds his business on a third party service, things may become uncertain as you do not have any influence on the existance of that service.

You can read more about the move in the 3D Modeling for Google Earth & Maps Community announcement.