There is now (for r2009) a Google Earth plugin available directly from Autodesk. It is available for subscription customers only.
To get it: Log into the subscription center. (If you are not the primary contact with Autodesk subscription sales for your company, you may have to ask someone else, such as your CAD manager, to do this.)
On the main Subscription page, you should see, in the center column, a list of "Product Information & Downloads".
Find the link for "Architecture, Engineering, & Construction (AEC): Product Modules and Add-ons"
In the list for Revit 2009 is the "Globe Link" plug in. "Globe Link" is the Google Earth plugin.
Joe