When iOS 5 launched last year, Apple sent the world a very strong statement: It wants to embrace social media, but in its own way.

We can now consider Thursday's developer preview of Mountain Lion, the latest version of Apple's desktop OS, an addendum to the company's social-media philosophy. Both iOS and Mountain Lion contain built-in Twitter functionality, giving users the option to tweet from virtually every nook of the Apple hardware ecosystem. And both operating systems now have iMessage, Apple's proprietary communication system that allows iOS 5 users (and soon, Mountain Lion users) to send messages without relying on traditional SMS.

But a bigger, bluer presence is conspicuously absent from Apple's OS integration. Facebook is the dominant player in social media, but its direct integration is nowhere to be found in Apple's desktop and mobile operating systems. It's a glaring omission considering Facebook updates are a simple drop-down menu choice in Android and Windows Phone.

The reason for the diss is simple: Apple doesn't want to hand over the keys to its social media car to such a large competitor. Apple is happy to integrate Twitter across iOS and Mountain Lion, sure. But as Ross Rubin of NPD Research told me, "Unlike Google, Twitter isn't making a competitive phone platform."

Twitter integration, of course, is a no-brainer for Apple. With less than half the user base of Mark Zuckerberg's 845-million-strong social behemoth, Twitter's reach pales in comparison to Facebook's. Furthermore, Twitter has begun shifting its product positioning – it's now less a social network than a self-described "real-time communications network."

In short, out of the world's three major social platforms – Facebook, Twitter and Google+ – Twitter is both the least threatening and most independent. Think of it as the Switzerland of information sharing.

Let's look at this broadly in terms of competition and threat to Apple's own platform aspirations, focusing on Google+ first.

Google is Apple's main nemesis in the mobile OS space, and has doubled down on its own social network by tightly integrating Google+ with Android. Yes, there's a native Facebook application for Android, but users wouldn't stand for an Android phone without Facebook functionality, and Google knew it. Thus Facebook integration appears in Android – but it's not as tightly integrated as Google's own Google+ service.

Google's native Google+ app for Android, for example, can default to uploading all of the photos taken on your Android phone to your Google+ account in the cloud. It's an incredibly easy process that promotes Google+ updates over Facebook updates.

But unlike Google, which had to embrace Facebook, and has its own social media platform, Apple doesn't have such luxuries. It's social media partner needs to be benign.

And unlike Facebook, Rubin reminds us, Twitter isn't an app platform either, which would otherwise present another huge point of contention and competition for Apple. Facebook debuted its open graph platform earlier in the year. It's a veritable call to arms for developers to weave their apps into Facebook's very fabric. With Facebook's single API, developers are able to integrate their apps into Ticker, Timeline, Newsfeed and other high-visibility areas of Facebook's interface.

And there's yet another pain point for Apple: Facebook is threaded deeply into Microsoft's Windows Phone OS, another competitor, albeit a smaller one. There's also the little matter of Microsoft's major investment into Facebook via Bing search integration, a partnership that could have Apple wary of Facebook's bedfellows.

But beyond ties to other competitors, the biggest warning sign for Apple could lie in the very stuff that makes Facebook what it is: data.

"User data tends to flow into Facebook easily," Gartner Research analyst Michael Gartenberg told me. "But it doesn't tend to come back out as easily." Imagine the rich treasure trove of data derived from millions of new Macs if Facebook were integrated with Mountain Lion. While the increased ability to share could improve the Mac experience for users, it would also bolster Facebook's vast stockpile of data. With richer data comes better opportunity for targeted advertising.

And with more ad dollars, Facebook grows into and even stronger force to be reckoned with.

Add to that rumors of a Facebook phone in the works, and Apple doesn't need any more reason to strengthen its competitor.

So in the end, Apple is left with only Twitter, or what Gartenberg calls "more of a news service for information dissemination." Now, of course, all of this could change when Mountain Lion makes its public debut come summer time. Apple and Facebook could reach an agreement to bring full Facebook integration to OS X, just as they almost did with iTunes Ping. It's proof that the companies are talking, and have reached at least some terms of agreement in the past. Perhaps another detente is on the horizon.

Or perhaps Apple, as typical, will keep doing its own thing.

*Facebook and Apple declined to comment for this article. *