The Atlantic recently wrote up a nice piece on Google Maps. It explores just how complex the whole operation is, how many humans and machines are involved in making Google's maps...
http://www.theatlantic.com/technology/archive/2012/09/how-go...
http://www.theatlantic.com/technology/archive/2012/09/how-go...
See e.g. http://blog.telemapics.com/?p=394