Google Maps feature request: add time dimension?

Wouldn't it be nice if Google added an extra dimension to Google Maps? One that would allow us to "go back in time" and see the previous versions of the maps?

Here is what I have in mind. Say, I want to see how a forest, a city, a glacier, the south pole or my neighborhood has changed over time. I navigate to the map I'm interested in and then, I go back and forth in time (actually, older versions of the same map) by sliding the "time control" much like I would zoom in or out.

I you like the idea, spread it out!