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The mystery of the disappearing Facebook-Ping integration

On Wednesday, Apple said users of its music social network could find friends via Facebook. But the feature has vanished, apparently over a tiff between the companies.

After Apple introduced its social music discovery service, Ping, on Wednesday, some people reported they were able to use Facebook Connect to find people to follow. But a day later, that feature doesn't appear to be supported by Facebook. And a lot of people are wondering why.

"Last night before going to sleep, I downloaded iTunes 10 and set up my Ping account (more on that later). As part of the setup, I signed up with Facebook Connect so I could find my social graph, ready to recommend songs," Om Malik, founder of GigaOm, wrote Thursday. "I woke up this morning, and expected to see Ping activity in my Facebook account, and well let's just say, nothing is going on."

According to Malik, Ping is not communicating with Facebook and vice versa.

So what happened? It was there Wednesday, and even made a cameo at Apple's presentation, according to screenshots captured from the live stream. One slide clearly says "find friends via Facebook or e-mail."

Once you sign up for Ping, you get a welcome e-mail from Apple, the text of which refers to finding friends through Facebook (see below). Yet people who logged in to the service Thursday only have the option to find new friends via e-mail.

The confusion seems to stem from some disagreement between Facebook and Apple. The reason, as articulated by Apple CEO Steve Jobs in an interview with AllThingsDon Wednesday: Facebook wanted "onerous terms that we could not agree to."

It's not clear what those terms were, as he did not elaborate.

Facebook didn't offer any hints, either. When asked about Jobs' comments, the company issued this statement: "Facebook believes in connecting people with their interests and we've partnered with innovative developers around the world who share this vision. Facebook and Apple have cooperated successfully in the past to offer people great social experiences and look forward to doing so in the future."

That leaves the door open for possible Facebook-Ping integration at a future date. But for now, Ping and Facebook are still on unfriendly terms.

Update 3:05 p.m. PDT: The word is that Facebook may have pulled the plug on the Ping integration at the last minute.

AllThingsD hears from unnamed sources that Facebook blocked Apple's use of the Facebook API within Ping "since it violated its terms of service." As a result, Apple reportedly then killed the advertised find-Ping-friends-via-Facebook feature.

Facebook's API is generally open for anyone to use, but there are a few rules. The company's developer agreement states that if an application exceeds more than 100 million API calls per day, "please contact us as you may be subject to additional terms." Apple says there are 160 million iTunes customers--and therefore potential users of Ping.

It seems those "additional terms"--whatever they were--are the "onerous" ones Jobs referred to.

Update 4:55 p.m. PDT: A Facebook spokeswoman wouldn't confirm whether the company had disallowed Apple's use of the Facebook API, but did say this: "We're working with Apple to resolve this issue. We've worked together successfully in the past, and we look forward to doing so in the future."