Udi Manber is Google's VP in charge of search quality, and Popular Mechanics has published a rare interview with the computer scientist. It's always interesting to learn how key people at the 'plex see the big picture - because their point of view is otherwise something we can only guess about. They also can confirm (or explain in more detail) things we've been puizzling over.
Along those lines, here's one answer that I particularly appreciated: the idea of "adding diversity" to search results.
...Iíll give you an example of something that came last week. We were evaluating a certain algorithm that adds diversity to the result. We did live experiments, which means we launched the algorithm to a very small percentage of users and then see how that compares to the result without the algorithm.