Here's one particularly creative example, courtesy of the Marginal Revolution blog.
By 2007, Google knew enough about the structure of queries to be able to release a US-only directory inquiry service called GOOG-411. You dialled 1-800-4664-411 and spoke your question to the robot operator, which parsed it and spoke you back the top eight results, while offering to connect your call. It was free, nifty and widely used, especially because – unprecedentedly for a company that had never spent much on marketing – Google chose to promote it on billboards across California and New York State. People thought it was weird that Google was paying to advertise a product it couldn’t possibly make money from, but by then Google had become known for doing weird and pleasing things...
What was it getting with GOOG-411? It soon became clear that what it was getting were demands for pizza spoken in every accent in the continental United States, along with questions about plumbers in Detroit and countless variations on the pronunciations of ‘Schenectady’, ‘Okefenokee’ and ‘Boca Raton’. GOOG-411, a Google researcher later wrote, was a phoneme-gathering operation, a way of improving voice recognition technology through massive data collection.
Three years later, the service was dropped, but by then Google had launched its Android operating system and had released into the wild an improved search-by-voice service that didn’t require a phone call. You tapped the little microphone icon on your phone’s screen – it was later extended to Blackberries and iPhones – and your speech was transmitted via the mobile internet to Google servers, where it was interpreted using the advanced techniques the GOOG-411 exercise had enabled. The baby had learned to talk.Well played, Google. Very well played. The author goes on to wonder what might be possible if Google turned its voice recognition software loose on its massive library of YouTube videos, thereby making it possible to create an instant transcript of every video in the YouTube galaxy.
Pretty amazing when you think about it. Also mildly creepy. Just remember, whatever you're doing... Google knows about it.