[EDIT 2008: Google removed the ability to open the GEC layer folder so all the placemarks appear under the same layer. The placemarks are still useful, but it makes it harder to view the information in a categorized fashion and reduce the clutter. Hopefully they will return to a more organized sub-layer format.]
[EDIT January 31, 2006: changed the story to reflect the current name of this layer: Google Earth Community Layer, and to reflect some of the improvements to the clutter problem.]
Layers are the links to Google Earth’s databases of place marks including dining locations, roads, railroad tracks, etc. Right now, many of the layers of data are pretty much confined to the US (although many countries have the Roads layer and Airports layer). Over time they will add other countries to the different layer types.
Some beginning users are slow to notice the Google Earth Community (GEC) layers. These layers simply a database of placemarks which were posted by people in the forums with a link back to the post if you open the placemark. As people discover things, they post a placemark about it at the Google Earth Community. Then a month or so later, Google processes these placemarks and adds them to the GEC layers.
When you select the Google Earth Community layer, and start zooming in to areas, you will see these blue “i” icons appear and labels naming the place mark. They mark points of interest to people who have posted in the forums. You can click on the “i” icon and see a link to the post (usually it says “more”). This links you to the post and possibly more details about that placemark.
The GEC layer can be a truly unique and interesting way to learn things about places all over the Earth. I highly recommend you try it out. You will learn things you never knew about places all over the world, or just find interesting things captured by the satellite photos and aerial photography used in Google Earth (like military jets in flight).
Since Google Earth was released, the Keyhole/Google Earth Community has grown by leaps and bounds. When this layer was first created there were probably a few hundred place place marks. Right now, there are probably over several hundred thousand, and it’s only going to grow. There are several threads of discussion about the growing clutter of the GEC Layer (see this one for example). Many people are making posts in the database pointing out the same thing (I think there are 10 posts about the US National Monument already). Some ambitious people are creating place marks of every building in their town or city. Several cities already appear very cluttered when you turn on this layer.
[EDIT: 6-November-2005 - Google has added a new layer called "Google Earth Community (unranked)" which stores a lot of the less-effective placemarks. And has added some sub-folders to the main GEC layer to help give you more control over what placemarks you see.]
The Google Earth database people have posted that they are working on the issue. It’s safe assume that the masters of a huge database like Google will come up with some good solutions to the growing problem. Perhaps they will break down the layer according to topic types in the forums [yes, they did this], or maybe they will use the ranking system. I hope they do something before they update the next database. In the last 30 days there were about 40,000 new posts on the web site.
But, even with the clutter, I highly recommend you use the GEC layer and learn more about the world and use it to find interesting or exciting new places.