Facebook has made a move that aims to protect against criticism that it's not protecting user privacy, while also giving users an option to embrace the opposite of privacy—very public posts.
Here's the public news: Teens will also be able to post publicly on Facebook, and turn on a "follow" button so other people can follow their public posts, and have them show up in news feeds. While Facebook has built its billion-plus user business around sharing privately, with people you already know, the company is increasingly making a push to foster public conversation, like Twitter.
(Read more: Twitter Q3 results: Growing revenue and net losses)
Facebook acknowledges that these changes are designed to capture the attention of fickle teens and compete with other services. In its blog announcing the news, Facebook says, "This update now gives [teens] the chance to share more broadly, just like on other social media services."
For the past year, the social network has faced concerns that it is losing its "cool factor" with teens, who are spending more time on Twitter, Tumblr (YHOO), WhatsApp, SnapChat, or Instagram, which is owned by Facebook. In the past two earnings conference calls Mark Zuckerberg and COO Sheryl Sandberg have addressed these concerns, saying they're flat-out not true, and trotting out a bunch of stats to illustrate how they're a nonissue.
Here Facebook is making a lot of noise about how "these changes are designed to improve the experience for teens on Facebook." It's clear Facebook is trying to drive more Twitter-like behavior. We'll see what other kinds of changes it makes to keep those fickle, influential teens hooked in light of so many alternatives.
—By CNBC's Julia Boorstin. Follow her on Twitter: @JBoorstin.