Oct. 15: This story has been updated to reflect new reporting.

Facebook hit the one-billion user mark last week, a little more than two years after it reached 500 million users. To mark the occasion, we've rounded up some of the best reads on Facebook and privacy.

When the Most Personal Secrets Get Outed on Facebook, The Wall Street Journal, October 2012

Two University of Texas students who didn’t want their fathers to know they were gay thought they had taken advantage of Facebook’s privacy settings. But their fathers found out anyway when the president of Queer Chorus, a campus choir they belonged to, added them to Queer Chorus’s Facebook group and Facebook automatically published a public notification. "Our hearts go out to these young people," Andrew Noyes, a Facebook spokesman, told the Journal. "Their unfortunate experience reminds us that we must continue our work to empower and educate users about our robust privacy controls."

Facebook Raises Fears With Ad Tracking, The Financial Times, September 2012

Facebook has been working with a company called Datalogix to track how often people who see ads for a given product on Facebook end up buying it in real-world stores. Datalogix does this by matching up the email addresses tied to users' Facebook accounts with troves of email addresses and other data it has purchased, much of which comes from customer loyalty cards and other programs. The company has data on 70 million American households from more than 1,000 retailers, including drug stores and grocers.

Facebook Sells More Access to Members, The Wall Street Journal, October 2012

In addition to its work with Datalogix, Facebook has started letting advertisers target users based on their email addresses, their phone numbers and the other websites they've been visiting. Gokul Rajaram, who oversees Facebook's ad products, said the changes were made "in a way that respects user privacy."

Facebook Confirms It Is Scanning Your Private Message for Links, The Next Web, October 2012

Last week, a Polish startup called KILLSWITCH.me posted a video to the website Hacker News that seemed to show that including link to a website — say, Mashable — in a private message to another Facebook user would include the "Like" counter on Mashable's website. Facebook confirmed to The Next Web that it was doing this, though it said it was not revealing any of users' private information.

Should Employers Be Allowed to Ask for Your Facebook Login?, The Atlantic, February 2011

When Robert Collins applied for a job with the Maryland Department of Corrections, the organization required him to give them his Facebook password. The Department of Corrections backed down after the American Civil Liberties Union sent a letter calling the practice "a frightening and illegal invasion of privacy," but it hasn't stopped elsewhere. California became the latest state to ban it last month.

Why Facebook Is After Your Kids, The New York Times Magazine, October 2011

The Children's Online Privacy Protection Act, which bars websites from gathering data about children under 13, means that 12-year-olds can't legally use Facebook. Mark Zuckerberg wants to change that. "That will be a fight we take on at some point," he said. He may not be successful. The Federal Trade Commission pushed new rules last month to make it harder for companies to track children online.

Germans Reopen Investigation on Facebook Privacy, The New York Times, August 2012

In August, the German data protection commissioner in Hamburg — yes, the Germans have a data protection commissioner — reopened an investigation into Facebook's huge database of human faces culled from users' photos. (Johannes Caspar, the commissioner, had suspended the inquiry in June but reopened it when Facebook failed to cooperate.) The database is a component of facial-recognition technology that allows Facebook to automatically detect users' friends' faces in the photos they upload to Facebook. The company has since agreed to get rid of it for users who live in the European Union.

The Face of Facebook, The New Yorker, September 2010

Jose Antonio Vargas's profile of Zuckerberg details some of his views on privacy, which the Facebook founder calls a "third-rail issue" online. "A lot of people who are worried about privacy and those kinds of issues will take any minor misstep we take and turn it into as big a deal as possible," he said.

Zuckerberg: Facebook 'Made a Bunch of Mistakes' on Privacy, Mashable, November 2011

Facebook is now required to respect users' privacy and undergo regular privacy audits for two decades, thanks to a settlement between the Federal Trade Commission and the social network last November. It also requires that Facebook pay $16,000 a day for each violation of the agreement. In a blog post the day the settlement was announced, Zuckerberg apologized for making "a bunch of mistakes" on privacy issues, including its now-defunct Beacon advertising platform and a number of changes made in 2009.

Facebook to Target Ads Based on App Usage, The Wall Street Journal, July 2012

Facebook is also taking steps to track users on mobile devices, likely the next frontier for online privacy. "The social network is tracking the apps that people use through its popular Facebook Connect feature," the Journal reports, "which lets users log in to millions of websites and apps as varied as Amazon.com, LinkedIn and Yelp with their Facebook identity." Facebook uses that data to help target ads. When the Journal's story ran in July, the company was also considering tracking what people do on the apps. (We reached out to Facebook to see what the decided, but they did not respond to requests for comment.)