The more people you’re connected to on the site and the more “likes” you post, the more ads can be personalized — hey, buy these shoes because your three friends did! — and the more potential advertising dollars can be generated. Facebook encourages widespread sharing by making the default settings for an adult’s Facebook page public to all. The site has made a concession when it comes to teenagers: the default setting allows basic personal information (name, networks, photo) to be public, while posts are shared with Facebook friends and also the friends of those friends. My son is too young to be on Facebook, but imagine that after his bar mitzvah, he posts photos of it. Along with the 300 people he knows, he could have an audience of 1,000 or more friends of friends he doesn’t.

As Zuckerberg put it in a radio interview: “We help you share information, and when you do that, you’re more engaged on the site, and then there are ads on the side of the page. The more you’re sharing, the more — the model all just works out.” Default settings are particularly important to this vision because most people (and especially teenagers) never change them. A recent Columbia University study of 65 college students found that 94 percent were sharing personal information on Facebook that they had not intended to make public.

It’s true that Facebook has taken action against the graver dangers of sharing. For example, the site is using a new technology to find and remove child pornography, and it’s a partner in the police’s Amber alert system for missing children. In September, Facebook started testing a special e-mail address with a small group of principals and guidance counselors that gives schools an inside track for urgent reports on bullying and fighting. These steps on behalf of kids are all good. They also don’t get in the way of all the sharing that makes Facebook prosper. Changing privacy settings for teenagers would.

For Zuckerberg and others in Silicon Valley, the assumption is that nonstop sharing, at every age, is inevitable. A week or so after Zuckerberg said he was ready to fight Coppa, Larry Magid, a co-director of the nonprofit ConnectSafely, seconded the idea in a blog post called “Facebook Ought to Allow Children Under 13.” Magid argued that given the millions of young kids already on Facebook despite the law, we’re better off letting them on legally and then hoping Facebook comes up with stricter privacy controls. Stephen Balkam, who runs another nonprofit, the Family Online Safety Institute (FOSI), similarly inveighed against “techno-pessimists” in his blog on The Huffington Post when Facebook’s geolocation service, called Places, met with a wave of criticism over privacy last year.

Magid and Balkam’s groups are both on what Facebook calls its “safety advisory board,” which the company has said is “independent.” Yet they also receive financing from Facebook as well as from other media companies. (FOSI receives $30,000 from each of 15 of its corporate sponsors, including Facebook; Magid did not disclose how much his group receives from Facebook and 15 other sponsors.) In September, Facebook held a reception on Capitol Hill at which the safety board members stood alongside Facebook reps promoting the company’s work on privacy, and Balkam lauded Facebook’s “remarkable maturity.” As a commentator on a CBS radio show and a columnist for The San Jose Mercury News, Magid sometimes criticizes the company but has defended it at key moments. (Headlines: “Online Privacy Concerns Often Misplaced” and “Facebook Privacy Lawsuit a Jumbled Mess.”) Magid discloses his financial link to the company because, he says, he can understand a potential conflict. On his Huffington Post blog, Balkam does not.