Well, with their new IPO looming, it would seem that Facebook is making strides to diversify a bit more. They recently announced that they are starting their own app store. The Facebook app store will be called, "The App Center," and will be launched within a few weeks. Here's a quote from the company,

“The App Center is designed to grow mobile apps that use Facebook – whether they’re on iOS, Android or the mobile web. From the mobile App Center, users can browse apps that are compatible with their device, and if a mobile app requires installation, they will be sent to download the app from the App Store or Google Play.”
This seems almost like an "aha moment." It makes you wonder why no-one thought of that before, especially considering that Facebook has over 900 Million users. That's almost a billion potential customers that you already are servicing. It seems like a no-brainer...

Source: Facebook Dev Blog