I spent about half an hour just plying with this program. Finding my house, my friends houses, places I have been in the world, places I want to go. It is increadible and makes me want to travel to so many places!!
Using this as a teaching tool would be quite difficult as most students would want to do what I did straight away, which is look up their house and so on. Assigning it as a homework assignment may work as students will have time to play with it and then complete the task. Using it within a set time period in the classroom may become hetic as students can easily become distracted.
Definitely something that I want to work into my lessons and as a tool to expand on the students learning experiance so far!
References: Google Earth, http://earth.google.com/