Google showcases a few of their own sites that have become responsive here in their google webmaster blog post. They explain the need they had from watching their analytics and walkthrough some other decision made in going responsive!
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Responsive design – harnessing the power of media queries
Webmaster Level: Intermediate / Advanced
We love data, and spend a lot of time monitoring the analytics on our websites. Any web developer doing the same will have noticed the increase in traffic from mobile devices of late. Over the past year we’ve seen many key sites garner a significant percentage of pageviews from smartphones and tablets. These represent large numbers of visitors, with sophisticated browsers which support the latest HTML, CSS, and JavaScript, but which also have limited …