One thing that was not documented fully at Google for integrating Google Earth into Google Map is that the function, getEarthInstance, is only available in the newest version of the Map API. I could not find exactly which version so the best way is to use v=2.x like in "http://maps.google.com/maps?file=api&v=2.x&key=yourkey" instead of specifying an exact version. Have fun with this new feature.

Google just added a new Earth plugin feature to Google Maps.  Now we can have all the functionalities of Earth as one of the selections buttons on Maps just like Satellite view.  This is a very exciting new development.