Many Web users have little idea about how, or when, they're being tracked. In this 2011 photo, Max Schrems of Austria sits with 1,222 pages about his activities on Facebook — the company gave him the file after he requested it under European law. Ronald Zak/AP hide caption

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Employers have been asking for prospective employees' Facebook username and passwords to do some extra research on whom they may be hiring. Leon Neal/AFP/Getty Images hide caption

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Wouldn't you love to know what she's jotting down? Of course you would. hide caption

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Facebook is on the verge of adopting new "opt in" privacy settings, according to reports. Here, company founder Mark Zuckerberg speaks during a visit to Cambridge, Mass., Monday. Darren McCollester/Getty Images hide caption

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Facebook CEO Mark Zuckerberg delivers a keynote address at the Facebook developers conference in San Francisco on April 21. Marcio Jose Sanchez/Associated Press hide caption

itoggle caption Marcio Jose Sanchez/Associated Press