One of Google's more clever, I think, ideas to collect data to boost that competitive advantage is GOOG-411. They provide, for free, telephone directory assistance. Why? From Wikipedia: "Google has stated that the company originally implemented GOOG-411 to build a large phoneme database from users' voice queries. This phoneme database, in turn, will allow Google engineers to refine and improve the speech recognition engine that Google uses to index audio content for searching."
Specific to Chrome, having the data collection built into the browser lets them even reach into the address bar of the browser for data, which I'm sure is a gold mine of valuable search related info for them for them.