Matt Cutts on How Google Tests Its Algorithms (Jennifer Slegg)

Have you ever been curious about how Google decides which algorithm is better than another, when they're pushing out one of the many tweaks they do weekly? How do they judge which tweak actually produces better results and which produces lots of good results? Or does the spam team just wave a nerf bat over the server before hitting a big red button and hope for the best? (searchenginewatch.com)