Facebook is relaxing its rules for teenagers. The 13- to 17-year-old set now has the option to share photos, updates and comments with the general public on Facebook. That means strangers, and companies collecting data for advertisers and marketing companies, will be able to see select posts. Teenagers will also be able to turn on the Follow feature for their profiles, which would allow anyone they're not friends with to see their public posts in the main news feed.

The changes will take effect immediately, the company announced in a blog post. The new setting might help Facebook compete against other social networks that skew younger, and having public data on teens will also help the company appeal to advertisers.

The social network is trying to balance the less strict settings with two other privacy protections. When new underage users sign up for a Facebook account, their posts will be shown to a more limited audience by default -- only to friends instead of friends of friends. If a teen decides to change the setting to Public, she or he will see a pair of pop-up warnings explaining what "public" means. One warns they could end up "getting friend requests and messages from people they don't know personally." Default settings for existing teens with profiles won't change or affect past posts.