Nude Webcams and Diet Drugs: the Facebook Ads Teens Aren't Supposed to See

Young Facebook users are sometimes exposed to ads inappropriate for them and the ads highlight Facebook's challenge in policing a social network that has more than a billion users and a million advertisers, by its count.

Facebook generated roughly $7 billion in Internet advertising last year, more than any other company except Google. One issue for the social network -- as well as for advertisers and for parents -- is that some young teens exaggerate their ages in their Facebook profiles. Thirteen is the minimum age to join Facebook. The situation is compounded by Facebook's social advertising system, in which users who click to "like" an ad can be featured as having "liked" it in future versions of the ad shown to their Facebook friends. And once they "like" an ad for a Facebook page, they will receive updates from that page. Advertisers on Facebook can set their ads to reach all users or narrow the focus. Facebook's website says it can help advertisers target consumers based on an array of user information it collects, such as age, gender, relationship status, politics and type of phone owned.