President Obama’s Twitter account, which is run by his “Organizing for Action” staff, follows 636,000 accounts. Many of them you might expect: Michelle Obama, Joe Biden, John Kerry. Even Mariah Carey and Snoop Dogg don’t really raise an eyebrow. But several accounts on the presidential follow list fit a different theme: Asa Akira, a porn star who has 653,000 followers and, in her Twitter bio, states “I have an award-winning asshole.” Joanna Angel (390,000 followers), who describes herself as a “multiple award winning punk porno princess;” Penthouse Pet Of The Year Nikki Benz (808,000 followers); and Ashley Steel (138,000 followers), who writes that she is a “Porn Star, Doggy mama, Happiness Junkie, XXX Model, Buddhist, & Total nerd.”

So why is the official Twitter account for the president of the United States publicly following adult movie stars? Of course, American porn stars are just as American (and just as worthy of the President’s ear) as anyone else, but this interaction is nonetheless an unusual move for an elected official’s campaign-managed social media account.

Neither the Organizing for Action campaign nor the White House immediately responded to a request for comment. A spokesperson for Joe Rospars, Obama’s principal digital strategist for both presidential campaigns, said that he was not available to comment.

The most likely culprit is a piece of Twitter etiquette known as the “follow back.” Some consider it polite to follow your followers, and until recently, only Twitter accounts that followed each other could communicate through direct messages, which added a practical component to the tradition. Twitter once had an “auto-follow” feature that handled this process on behalf of users by automatically following any new followers. Twitter removed that auto-follow feature from its own site in 2009, but the capability stuck around in its API until 2013, allowing many third-party tools to set accounts to “auto-follow” regardless.

Even if a social media agency or volunteer had controlled for variables like number of followers, which can indicate the legitimacy of an account, it wouldn’t necessarily have filtered accounts from, say, popular porn stars.