Why did Facebook fall out of Apple’s Mountain Lion?

July 26, 2012, 12:02 PM UTC

FORTUNE —  First Ping, now Mountain Lion. You have to ask, what is it with Apple (AAPL) and Facebook (FB)?

Let’s review.

Remember when Steve Jobs promised two years ago at the launch of iTunes Ping —  Apple’s failed experiment in music social networking — that thanks to its tight integration with Facebook you would be soon be able to see what songs your “friends” were listening to and vice versa?

Well, the Facebook connect feature Jobs demonstrated on Sept. 2, 2010, had disappeared by Sept. 3. Ping went on to suffer what even Tim Cook now admits was a slow death. It will reportedly be removed from life support this fall with the next release of iTunes.

“facebook” is now missing from this list

Now something eerily similar has happened with OS X 8, the latest version of the Mac operating system. Journalists posting reviews of  Mountain Lion’s long-awaited Facebook sharing feature say that it works like a charm. Just use the Share button “and with a few clicks,” Apple’s promo copy promises, you can “post straight to Facebook.”

But though Facebook integration was provided as a separate installer in the Mountain Lion preview handed Apple developers on Monday, June 11, it was not part of the version released to the public on Wednesday, July 25.

Instead, Apple’s What’s New page marks the Facebook feature with small yellow triangle that says “Coming this fall” and a tiny footnote which, if you scroll all the way to the bottom of the page, says the same thing.

What happened?

The speculation among developers is that Apple and Facebook agreed for reasons unknown to wait for the release of iOS 6, also scheduled for this fall.

But you never know what’s going on behind the scenes. You may recall that Steve Jobs told an interviewer after the Ping integration fell through that Facebook wanted “onerous terms that we could not agree to.” When asked if, despite these disagreements, the company might still consider implementing Facebook Connect, Jobs just shrugged and said “We could, I guess.”

They never did.

This time, Facebook is reportedly taking its commitment to Apple more seriously. According to the
New York Times
, the company is finally rewriting from scratch its notoriously sluggish iPhone app and, according to Bloomberg, has even hired some former Apple engineers to do the job.

But Apple seems to be taking nothing for granted. Reviewing the report we filed from WWDC last June, we note that although Facebook integration was one of the 12 new features demoed in Scott Forestall’s iOS 6 keynote presentation, it was omitted altogether from Craig Federighi’s preview of Mountain Lion.

Rather than repeat Steve Jobs’ mistake, Federighi seemed careful not to promise a Facebook deal he couldn’t yet deliver.