A worker sits in the Facebook office in Menlo Park, Calif. The amount of information Facebook learns about its users seems to have entranced Wall Street. Jeff Chiu/AP hide caption

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Investors will be betting that Facebook won't make its users so uncomfortable over privacy that they quit. Photo Illustration: Joel Saget/AFP/Getty Images hide caption

itoggle caption Photo Illustration: Joel Saget/AFP/Getty Images

A photo illustration shows the photo-sharing app Instagram's fan page on Facebook's website. Facebook is acquiring Instagram for some $1 billion. Justin Sullivan/Getty Images hide caption

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Analysts say that to succeed, Facebook needs to figure out how to sell ads on mobile platforms. Saeed Khan/AFP/Getty Images hide caption

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Facebook co-founder and CEO Mark Zuckerberg at Facebook headquarters in Palo Alto, Calif., in 2007. The company is expected to file papers for an initial public offering this week. Paul Sakuma/AP hide caption

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