A small number of Instagram users have seen Foursquare, the location-sharing network, replaced with Facebook Places in the Facebook-owned photo-sharing service. Facebook confirms that it’s testing the swap.

While it’s a small-scale move, it has a number of implications for Foursquare and Facebook—and anyone trying to map out the future of location on the Web.

Locating The Future

It’s nearly impossible to own the flow of social media, but if anyone could, it’s Facebook.

When Facebook bought Instagram for $1 billion in 2012, Mark Zuckerberg promised to let founder Kevin Systrom continue to run it independently. One example of that independence: The photo-sharing application exclusively used Foursquare’s application programming interface, or API, to tag photos with locations. Until now.

While Facebook failed to popularize a check-in feature that it launched in a direct challenge to Foursquare, it’s maintained its own directory of businesses and other points of interest, which people use to tag photos and status updates with a location. It also uses this directory to create pages for local businesses—a crucial part of its advertising offering.

The Facebook Places test doesn’t mean Facebook is ditching Foursquare entirely, but it could be the first step toward bringing more Facebook data in-house. Today, even if Instagram users don’t send their photos to Foursquare, they still share their location with the service, which improves the accuracy of Foursquare’s map data. 

“Foursquare is a great partner, and people will continue to be able to share their check-ins to Foursquare from Instagram,” an Instagram spokesperson told ReadWrite in an email. “We are constantly testing experiences throughout the app to provide the best possible user experience as part of future planning.”

We’ll spell out the implication of “future planning”: Foursquare today is privately owned, but it’s quite possible that it could be acquired by a Facebook competitor at some point in the future. One way to look at this test is some sensible scenario planning by Facebook.

WhatsApp, a messaging service which Facebook is in the process of acquiring, also uses Foursquare’s database of places today—which means Facebook has even more reason to worry about Foursquare’s fate.

And even if Foursquare remains independent, it has signaled that it hopes to make money off of its API. Already, Gnip, a data-mining service, and Microsoft pay Foursquare for access, and it’s reasonable to think Foursquare will aim to charge other high-volume services that use its API.

In that light, Facebook’s move could be seen as a negotiating tactic to preserve its free access or secure favorable financial terms from Foursquare.

Controlling The Flow of Content 

Besides the financial risks of losing Foursquare to a rival or having to pay up, there’s Facebook’s mobile strategy to consider.

With Facebook Messenger, Instagram, Paper, and WhatsApp, Facebook is building a flotilla of social apps to keep users in its orbit. It already requires users to click on a link in order to see Instagram photos posted on Twitter. By sending people to a Facebook Places page rather than a Foursquare venue, it could hold more sway over users.

As ReadWrite pointed out last year, big players like Facebook are seeking to control the lifeblood of the social Web—status updates, images, video, and check-ins—in the same ways rulers of ancient empires sought to dam rivers. It may be a grandiose goal, but you can’t blame them for trying.

Facebook is the one social network that could really choke off vast portions of this social flow. It has all the tributary rivers of data already: people, places, and photos.

Over one billion people use Facebook each month to share status updates with friends and family. Instagram has over 150 million monthly active users, and 465 million people use WhatsApp, Facebook’s newest addition to the family, each month. The only thing Facebook is missing to completely own social engagement? A well-used and hence accurate location service. 

Facebook Places, and other services like Google Maps and Yelp, have directories of businesses, but Foursquare excels in so-called “points of interest”—unique venues where commerce may not be transacted but memories are formed. Those quirky locations picked by users are the same kind of places where Instagram photographers snap pictures.

By jettisoning Foursquare in favor of its own data services, Facebook can finally tap Instagram’s users to add their memory-making places to the social network. 

Great For Business, Not For People

If Facebook controls the flow of information and works to keep users inside its own services, the social network will own even more of our online lives. 

I’ve said that Facebook is the last great social network, in part because it’s so big no one startup can overtake it. But it’s also because Facebook continues to stake claim to the aspects and information the make up our social identity, and forces us to rely on Facebook as the one social login that powers the Internet’s applications. 

It’s smart for Facebook to want to own location services. But the prospect of losing this tie to the Web’s open flow should give us pause. We can check in any time we like. But our memories can never leave.