No. 6: Facebook

Our relationship with Facebook? It’s complicated.

As anyone who’s seen the poster for the film “The Social Network” knows, Facebook made more than 500 million friends this year, including the Queen of England.

Friendship with the social networking giant, though, can come with an awful lot of conditions. When the year started, Facebook users had been racing to adjust their privacy settings after the company made changes it said would help control your experience. The “help” included making personal information such as name, photos, and status updates public — and searchable — by default. Watchdog groups representing everything from privacy to consumers (even the American Library Association) filed a federal complaint.

Considering the big blowup over Facebook’s ill-fated Beacon marketing snafu, some comforting words might have been expected from CEO Mark Zuckerberg. In January, the then-25-year-old Zuckerberg told TechCrunch’s Michael Arrington that privacy is “no longer the norm online,” and that if he were launching the site today, all information would be public by default.

Thus began a rocky year for the young mogul, fraught with lawsuits, privacy complaints, and public scrutiny, but also massive success. Which, come to think of it, was probably just like any other year for Zuckerberg. The company settled that pesky Beacon issue in spring, when a judge approved a $9.5 million settlement establishing a Digital Trust Fund. Then came further privacy backlash, including a call from several U.S. senators asking the company to change its policies, as Facebook launched its “instant personalization” feature.

The privacy battle became such a flashpoint that it made the cover of Time magazine in May. With tools like the new Friendship pages being touted as fodder for so-called Facebook stalkers, privacy battles are likely to continue into 2011.

None of that stopped the massive popularity of the site that loves getting into our business. Facebook’s pervasive influence had social scientists and psychologists studying its impact on how we interact IRL (in real life). Everything from romantic relationships to how we use language to our grades has been affected by our attachment to the social network. And only when the site went away — just for one Thursday afternoon in September (spurring plaintive searches on “Facebook down today“) — did we realize how much we needed it.

Not satisfied with finding friends or playing Farmville, some people put the site to innovative use in 2010. One Florida politician credits Facebook with his new job. A Canadian storeowner caught a thief. In England, a nurse used it to save a toddler’s life. Facebook itself tried its hand at predicting midterm election results.  Its new Facebook Places Deals lets partners like the Gap offer discounts and freebies to fans who check in on their phones. And its modern messaging system aims to change the nature of online conversation.

Zuckerberg, the site’s billionaire founder, was as much of an obsession for us as Facebook itself: A controversial post from Gawker turned the tables on Zuckerberg by siccing a photographer on him, then publishing photos of his home, girlfriend, and family. A viral campaign tried to “block” the CEO, though ironically that triggered a safety measure that made him unblockable.

And throughout 2010 we saw the build-up of that movie. Months before David Fincher’s film came out, people raised questions about the truth behind the site’s creation myth and the film’s portrayal of Zuckerberg as a touchy, socially awkward boy genius. Zuckerberg launched a low-key PR campaign against “The Social Network.”

When the film finally debuted in October, critics and audiences gave the drama a big “like”; reactions from new media types were more mixed. But Zuckerberg, who ended up seeing it, might’ve benefited from the “humanizing” cinematic profile. Plus, online searches for “Facebook sign-up” ricocheted up nearly 500 percent after the movie’s debut, and “The Social Network” is an Oscar frontrunner. That wouldn’t be a bad status update at all.

–Melissa O’Neil