Rashmi’s Blog: Google’s pragmatic, data-driven approach to user interface design: so at Google (being a data company with a huge customer base), they user test with data: make a small change, show it to a subset of users, and track the results. Amazon uses this approach too.
Also: “The “I am Feeling Lucky” button is not used much. But their focus group participants always tell them they like it, and ask Google not to remove it (even though these participants have never used that button, nor do they ever intend to use it!). So its not all rationality and data driven design at Google!”
Peterme also follows up.