Facebook is budging on Google's turf with its new graph search engine, and its impressive user base may add significant weight to its efforts.

Facebook's greatest achievement was to convince one million users, i.e. a seventh of the world's population, to put their personal lives online and share them for everyone to see. Now, the social network is moving to the next level, rolling out a search tool to make use of all that personal info. People may be growing more careful about what they share online, but the search graph aims to leave nothing hidden.

The social networking company unveiled its new search tool last week, and it is the work of former Google engineers. Facebook's algorithms will filter search results for each person, ranking the friends and brands it believes a user would trust the most. The graph search will initially mine users' interests, photos, likes, and check-ins, but it will later comb through other information as well, including status updates.

"While the usefulness of graph search increases as people share more about their favorite restaurants, music and other interests, the product doesn't hinge on this," Facebook spokesman Jonahan Thaw told the New York Times.

The engineers who created the tool, however, note that the project will not grow to its full potential if Facebook data is "sparse." On the other hand, Facebook is confident that users will share more data, and they probably will. After all, Facebook and Twitter are the most popular venues for bragging about one's lunch, haircut, events, locations, and so on. Facebook users tend to share just about everything.

Tom Stocky, one of the creators behind Facebook search, told the NYT that what people post on Facebook will prove useful when someone searches for those particular interests. In other words, people will become more useful to their friends by liking more things, he added.

"You might be inclined to 'like' what you like so when your friends search, they'll find it," said Stocky. "I probably would never have liked my dentist on Facebook before, but now I do because it's a way of letting my friends know."

Meanwhile, various independent studies indicate that Facebook users are growing more cautious about what and how much of their lives they share online, especially since employers now do their own research on Facebook.

Many companies have tried to make search more social, but none quite to Facebook's scale. Moreover, Facebook's new social search tool also marks a major step forward in what engineers call structured or semantic search. This type of Web search means that search engines not only understand keywords, but also how people, places, and things relate to one another.

At the same time, advertisers aiming to target more specific audiences also stand to benefit from graph search tools, and Facebook draws most of its profit from advertising. Plus, if people share more things and search for more data, automatically they spend more time on the site.

Facebook is, however, aware about privacy concerns as well. Upon announcing its new graph search tool, the company went to great lengths to assure that it would respect its users' privacy. People can always choose what to make visible and to whom, and Facebook encourages everybody to check their privacy settings. On the other hand, Facebook nixed an option that comforted many users: the option of remaining obscure when someone is searching for them. Now, nobody can stay hidden anymore.