Where will search go next? One answer to that question was provided by the billionaire double act of Sergey Brin and Larry Page, Google's founders, in 2004, when pressed about their vision of the future by the former Newsweek journalist Steven Levy.

"Search will be included in people's brains," said Page of their ambition. "When you think about something and don't really know much about it, you will automatically get information."

"That's true," Brin concurred. "Ultimately I view Google as a way to augment your brain with the knowledge of the world. Right now, you go into your computer and type a phrase, but you can imagine that it could be easier in the future, that you can have just devices you talk into or you can have computers that pay attention to what's going on around them…"

Page, generally the wilder thinker, was adamant, though. "Eventually, you'll have the implant, where if you think about a fact, it will just tell you the answer."

Nine years on, Brin's vision at least is already reality. In the past couple of years, a great advance in voice-recognition technology has allowed you to talk to search apps – notably on iPhone's Siri as well as Google's Jelly Bean – while Google Now, awarded 2012 innovation of the year, will tell you what you want to know – traffic conditions, your team's football scores, the weather – before you ask it, based on your location and search history. Page's brain implants remain some way further off, though both Google founders have lately been wearing "Google Glass" prototypes, headbands that project a permanent screen on the edge of your field of vision, with apps – cameras, search, whatever – answerable to voice-activated command. Searching is ever more intimately related to thinking.

Until now, Google has been an unprecedented signposter of knowledge. It has not "known" the answer to anything itself but it has had an awfully clever way of directing you to exactly the place you can find out. In some senses, that attribute is in the process of changing. This year, Google will roll out what it calls its Knowledge Graph, the closest any system has yet come to creating what Tim Berners-Lee, originator of the web itself, called "the semantic web", the version that had understanding as well as data, that could itself provide answers, not links to answers.

It is quite easy to get caught up in the utopian possibilities of the technology and quite easy, of course, to forget that Google has also created wealth faster and more efficiently than any company in history; that it is probably the most effective generator of advertising dollars ever invented; and that a great deal of what it knows about us we might well want it not to (an unease that might grow by association now that Facebook has announced a search engine of its own data, one that promises to be even more intimate in its revelation of personal history than Google has ever dared to be).

All the Google employees I speak to adopt the same kind of reflexive flinch if you hint at any of this, if you suggest that their motives for all this data gathering, this knowledge sharing, might be anything other than pure. It is the same kind of "Why wouldn't you trust us?" flinch that has powered the company's growth through loyalty and that sees it refuse to reveal its own intimate search history even when threatened, as it is currently by the European Union, to prove that it does not artificially weight algorithmic results in favour of its own products and commercial partners.

a great deal of what it knows about us we might well want it not to (an unease that might grow by association now that Facebook has announced a search engine of its own data, one that promises to be even more intimate in its revelation of personal history than Google has ever dared to be).