Google Earth has now been downloaded more than a billion times, according to the Official Google Blog. The number counts the "desktop client, mobile apps and the Google Earth plug-in."
To create an idea of the number, the blog gave some numbers to think about. "How large is one billion? One billion hours ago modern humans were living in the Stone Age. One billion minutes ago, the Roman Empire was flourishing. If you traveled from Earth to the Moon three times, your journey would measure one billion meters."
Google bought Keyhole in 2004 and slowly added features after it was relaunched as Google Earth in 2005. The product was used very successfully by Arcade Fire for their HTML5 music video for We Used To Wait, where you could add your address and it was rendered in to the video as the song played.
The program has had some controversy – areas of national security have been blocked in a number of countries and claims that terrorists are able to see details about potential targets has also been discussed.
That 1 billion number no doubt includes upgrades and people who have it on multiple devices but hundreds of millions of users at the least. The company has gathered a number of interesting usages and presents a separate site to display them, with the tag "One world. Many stories."