Well worth reading. Some excerpts as a teaser:
[Google Fellow Amit] Singhal notes that the engineers in Building 43 are exploiting ... the hundreds of millions who search on Google. The data people generate when they search -- what results they click on, what words they replace in the query when they're unsatisfied, how their queries match with their physical locations -- turns out to be an invaluable resource in discovering new signals and improving the relevance of results.Even so, this raises the question of where the point of diminishing returns is with more data and more users. While startups lack Google's heft, Yahoo and Bing are big enough that -- if they continuously experiment, tweak, and learn from their data as much as Google does -- search quality differences likely would be in an imperceptibly small chunk of long tail queries.
"On most Google queries, you're actually in multiple control or experimental groups simultaneously," says search quality engineer Patrick Riley. Then he corrects himself. "Essentially," he says, "all the queries are involved in some test." In other words, just about every time you search on Google, you're a lab rat.
This flexibility -- the ability to add signals, tweak the underlying code, and instantly test the results -- is why Googlers say they can withstand any competition from Bing or Twitter or Facebook. Indeed, in the last six months, Google has [found and] made more than 200 improvements.