Facebook allows marketers access to users email addresses & phone numbers.

Facebook in recent months has begun allowing marketers to target ads at users based on the email address and phone number they list on their profiles, or based on their surfing habits on other sites.
It has also started selling ads that follow Facebook members beyond the confines of the social network.
Rankling privacy advocates most, Facebook is using its data trove to study the links between Facebook ads and members' shopping habits at brick-and-mortar stores, part of an effort to prove the effectiveness of its $3.7 billion annual ad business to marketers.
Facebook hasn't said which advertisers participate in the studies. In principle, they allow a marketer like a shampoo maker to learn, in aggregate, how much viewing an ad on Facebook increases sales across a range of retailers.
"We have been working to make it easier for marketers to reach the right people at the right time and place," said Gokul Rajaram, who manages Facebook's ad products. He added the latest ad changes are done "in a way that respects user privacy."
At the core of Facebook's expanding ad strategy is the fact that the social network knows a lot about its users' true identities. While Google largely makes inferences about people based on their searching and browsing habits, Facebook is built on people volunteering personal information that's valuable to marketers, including names, friends, phone numbers and tastes.
In September, Facebook began allowing marketers with their own lists of email addresses and phone numbers to target ads at specific groups of Facebook users of at least 20 at a time. Facebook matches up that outside data with information users have entered into their profile.
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