He didn't elaborate, obviously, but you can see in Facebook's public documentation that Apple probably wouldn't have appreciated handing any more of its network over to Facebook than it did. All Ping seems to be at this point is a system of "liking" certain content (specifically on the iTunes Store, to the frustration of many of us who want to do it directly from our personal library of music), and if Facebook required that all of the "like" buttons went their way, you can see why Jobs wouldn't agree.
Turns out that even after Ping's launch, things got even more fractious between the two companies -- Apple did kick off Ping with the option to add friends with Facebook Connect, but Facebook blocked access when it was discovered that Apple wasn't playing by the rules. It's actually an open service, unless Facebook decides that it isn't, and apparently Apple's Ping network was an unwelcome guest with a lot of traffic since Apple didn't come to terms with FB ahead of time. Apple removed the service from Ping, but you'll still see some notes around suggesting you can bring in friends from Facebook.
So. Looks like Ping is already making a splash with much larger social networks. If Apple can build up its network without using Facebook's services, it seems much less likely that they'll find a way to share users in the future. As you can see above, Facebook is still implemented on iTunes, in the form of sharing albums and songs that you like, but it's completely separate from what's been built for Ping.
Despite the sour start to the social mixup between Ping and FB, Engadget suggests that conversations between the two companies are still ongoing. It may not be long before all this is a hearty laugh between friends.