Facebook has released a new iPhone photo app called Facebook Camera that allows users to apply vintage filters to their photos. Instagram, a popular service that Facebook purchased in April, also allows users to apply vintage filters to their photos. The new standalone service is "slick," but it makes for a "billion-dollar elephant in the room," says Mike Isaac at All Things D. "Why build another camera app when you just dropped a ton of cash on one?" What is Facebook getting at? Here, four possible theories: 

1. The Instagram purchase was purely defensive
Instagram was taking over mobile photos, says All Things D's Isaac. All the while Facebook was quietly working on its own dedicated camera app, and the social network "couldn't wait around and watch the company snap up every user." When word got out that Instagram was available, Facebook moved quickly to nullify the competition.

2. Standalone apps are the future for Facebook
"Facebook simply has too many features and tools to bundle into a single mobile app," says Lauren Indvik at Mashable. Releasing more nimble and specialized spin-off applications that lead back to the blue mothership is a "smart move," especially since the main Facebook app continues to get bigger and clunkier. Last year, for example, the company unveiled a dedicated Facebook Messenger app, and just released another called Pages Manager; Facebook Camera is a logical progression. Plus, these individual apps afford Facebook more opportunities to monetize the mobile market with ads, says Salvador Rodriguez at the Los Angeles Times. Expect more to come.

3. The two apps appeal to different users
Releasing another camera app may seem strange, says Nick Bilton at The New York Times, "but Facebook Camera is aimed at a different audience." Instagram has 40 million users, while Facebook has 900 million. "This leaves a large swath of people who are not on Instagram but are actively taking photos and uploading them to Facebook." There may not be as much overlap as critics assume. Not to mention the two services offer different features, says Ed Oswald at PC World. Facebook Camera lets users batch upload multiple photos versus Instagram's one-at-a-time method. As a result, "a majority of photos will come through unfiltered and not retouched" — very non-Instagram.

4. Facebook may merge the two... eventually
Facebook has said repeatedly that it will continue to let Instagram operate under its own brand, says Brittany Darwell at Inside Facebook. But if Camera takes off, "Facebook could ultimately merge Instagram with the app," combining the two applications' best features. Either way, having both at its disposal is a win-win for Facebook, says Oswald.