Is it possible to have Google Earth integrated into a Silverlight app? I've tried searching on Google but the best results I could find were forum posts from 2008 which were uncertain at best.
I don't believe there is any straightforward way to utilize Google Earth from a Silverlight application. And even if you could get it to work, you would have practically no control over the Google Earth portion of the program since, to my knowledge, it is not designed to be hosted in other applications.
However, if what you want is a 2D/3D GIS (Geographic Information System) inside your Silverlight application, an alternative to Google Earth is the Bing Maps Silverlight Control. This is already Silverlight compatible, has a full 2D/3D API and provides some of the same features as Google Earth.
Here are two links about the Bing Maps Silverlight Control:
As I recall, you have to apply for a free license to use this and there are some restrictions. Please read the license carefully.