Building structures in Second Life to prototype one's your going to build in real life is a trend most Architects I work with are somewhat resistant to - or at least, they're sitting on the fence on the issue (including building Architectural House Plans in Second Life which might help people decide if they want to purchase a plan, or live in it via Second Life first).

But now, the American Institute of Architects is doing something similar with Google Earth - as the video below shows from the Official Google Blog in a post called New 3-D layers from AIA on Google Earth.

 

How much farther would Google need to go to simply make Google Earth another Second Life?  Many have speculated that Google might have plans to do just that - but so far, the interface to Google Earth has a browser but not Avatars and no interactivity with others looking at the same properties/objects.
And yet, with a little imagination it's not far fetched to wake up one day and find out Google now has a Virtual 3D World of it's own you can interact with and move around in.
Meanwhile …
 "..Fly to America’s Favorite Architecture, a layer featuring the American public’s favorite architecture (as selected though a national poll announced earlier this year). View all 150 structures, including many with just created 3-D models of the buildings, ballparks, bridges, and memorials that characterize architecture in the eyes of Americans. And then explore the second layer, Blueprint for America. Blueprint is a community service effort funded by the AIA, in which AIA members donating their time and expertise are collaborating with community leaders and local citizens to enhance the quality of life in their community. You’ll be able to track the progress of these projects on Google Earth as they unfold over the next year and, we hope, become inspired to take action where you live. "
One thing that Google Earth would surpass Second Life or the other 3D Virtual Worlds -the structures in Google Earth would resemble actual landmarks.  And, I'm betting the interface to Google's 3D Virtual World would be an improvement over Second Life.