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It used to be the most private of times. Shut the door and you'd be alone to do your business. But according to new data, when you've got to go, social media comes along.

According to Nielsen's "State of the Media: Social Media Report," a third of Americans between 18 and 24 use social networking services in the bathroom. Yes, they are updating statuses or checking out their social feeds while sitting on the can. (More are still using social media in the boardroom than in the bathroom with 50 percent say they use social networking in the office.)

Of course, it's not an entirely new phenomena. People have been toilet texting and surfing the web on their phones in the bathroom for quite awhile. But it does illustrate another major finding in Nielsen's data - mobile social media use is up. Way up.

According to the annual report, time spent on Twitter and Facebook's apps and websites increased by 63 percent in 2012. Americans spent 27 billion minutes a month using the Facebook app and 3.6 billion minutes with Twitter's app.

And that sheds light on another finding: Facebook continues to be the most-used social network in the U.S. Seventeen percent of people's time at a computer is spent on Facebook.com, the report says. Twitter comes in second place, but Pinterest also rose over the last year. Nielsen's data reinforced that Pinterest is most popular with woman. Seventy percent of the site's users are women.

You can check out the full report here, but the main takeaway: we're on social media a whole lot, even when the bathroom door is shut.