Your right, On Google Earth is a building site where my house should be! (It was built last september)
It would be very expensive to have live feeds, and imagine the opportunities for the criminal/terrorist fraternity.
I seem to recall reading on the GoogleEarth site itself, that the images could be up to 3 years old. Since the program takes images from many sources and "knits" them together I would think it unworkable to have an "effective date" on your image.