new, automatic feature in Google Earth that helps keep your building models aligned to the ever-shifting and updating satellite imagery beneath it.
Sometimes you may get a message on your model preview page in the 3D Warehouse which reads, "Google Earth imagery has been updated. Please check your building position and update as required."
In this case you can manually shift the building to match the new (and usually more accurately placed) imagery. There is also a new icon to alert you which looks like a green arrow over a map.
My model (above) has been adjusted in this manner. I used the opportunity to update some of the building textures as well.
EDIT: It's a couple days later and the building model has in fact updated on Google Earth. But the "shifting imagery" notification is still appearing on the preview page.