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

itoggle caption Ronald Zak/AP

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. iStockphoto.com hide caption

itoggle caption iStockphoto.com

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