(Facebook.com)

So now the fourth of the big four has a its own app store. Facebook just launched the "App Center," described on its developer blog as "a new place for people to find social apps." In other words, it's a place Because Sims Social doesn’t already eat up enough of our time.

The “Facebook Platform” and therefore apps have been around since days of yore (i.e. 2007), but things have have never been, shall we say, particularly curated. Now apps will be rated, which at least offers a metric other than how many friends from grade-school summer camp have installed a given app and/or allowed it to post messages to their timeline. Nor will poorly reviewed apps make the cut for inclusion.

Here's what kinds of apps are eligible, as per the guidelines:

• An app on Facebook.com in a canvas page
• A mobile app built for the web, iOS or Android that uses Facebook Login
• A website that uses Facebook Login and has an immediately logged-in, personalized experience (see App Quality for more info)
• An App for Pages built to manage or enhance other companies’ Facebook Pages

The changes also open the door to paid apps:

Many developers have been successful with in-app purchases, but to support more types of apps on Facebook.com, we will give developers the option to offer paid apps. This is a simple-to-implement payment feature that lets people pay a flat fee to use an app on Facebook.com.

All this could also throw a monkey wrench right into the social marketing

But it's the mobile angle that's most interesting, in light of yesterday's S-1 amendment, which admitted outright the company's long-term concerns on the mobile front. The statement explains that,

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.

Seems like they've already got more than enough mobile Facebook users.