In the battle to conquer real-time search, Google has drawn a line in the sand. The search giant today went live with its Social Search feature, which adds relevant results from users’ social graph. But one thing is noticeably absent from those results — Facebook content.

Because so much of Facebook’s information is private, Google cannot access it. For a social network trying to plant its flag as the curator of personal content online, that could be a problem.

This week, Social Search moved from an opt-in Google Labs experiment to
a default feature on Google.com for signed-in users. Now Google searchers will see results from their friends on the bottom of search pages. Content from Twitter, blogs and other social arenas will be culled. But the feature can only access Facebook public profile pages, which means that the majority of information shared on Facebook will still be siloed on Facebook.

Microsoft announced in the fall that it would start including Facebook member status updates in its real-time
search results in 2010. But Facebook members
still can’t make their status updates available in the wider web. Google has
also expressed an interest in adding Facebook status
updates to its search results. But Facebook members have been cagey about sending more of their information to the open web.

Late last year, Facebook tried to shift its users toward sharing their personal information more freely, with privacy changes aimed at more sharing. Now when users click on the option to “share with everyone,” their content is supposedly available to Google. But not in social search. 

Maureen
Heymans, the technical lead for Social Search at Google, tells PCWorld
that if Facebook lets its members make more profile content public,
Google will consider adding it to Social Search query results.
Comprehensiveness is important to Google and Social Search is an effort
to improve the relevance of search results, so it makes sense that
Google would include them.

But
there’s still the pesky issue of user preference. And so far, consumers aren’t as willing to share their personal information as Facebook would like. For the social net, the content shared by its 350 million members worldwide is only as valuable as what it can be done with it.

The changes to the site’s privacy settings this fall set off an avalanche of critiques that are still coming in. And considering how
much information lies in Facebook profiles, consumers have not yet
signed off on sharing that data.

If Google users like Social Search and get sad about their information being stuck behind the wall of Facebook, they may give help Facebook in its efforts to achieve wider social relevance. But more likely, they’ll find services where they can share specific information publicly.