I believe they do a tonne of testing, this video from Google is a great illustration of their process: http://www.youtube.com/watch?v=J5RZOU6vK4Q http://www.yo

I believe they do a tonne of testing, this video from Google is a great illustration of their process: http://www.youtube.com/watch?v=J5RZOU6vK4Q http://www.youtube.com/watch?v=J5RZOU6vK4Q