If they had learned from the Newton failure to stay away from the PDA business, there would never have been an iPhone.
One could argue Newton was ahead of it's time and the tech failed it (the handwriting tech wasn't great, yet was one of it's touted features, source:
Wired).
As the case with Ping and Connect, there wasn't a ton of innovation there...it was just poorly executed. The value-add for Ping back in the day was very questionable for a consumer. For iTunes Connect, it made sense in theory, but the user experience was very poor and the "social networking" features were very limited (you could comment/like but that was about it).
With the latest betas of iOS, I'm starting to really question Apple's design philosophy when it comes to mobile devices. Google has slowly won me over with the consistency of their Material Design (even though things are starting to look bland), but at least there is a very visible effort at great user interfaces and experiences on mobile.
Someone mentioned iMessage and Photo/iCloud sharing (you can comment, like, etc in a closed-social network), which could serve as a great foundation for more public social networking. Taking a page out of Snapchat's playbook with their recent move to "replace the camera", Apple should do the reverse and build on top of the camera.
However, if they think "square" videos are the future ("One of the prototype designs for the unnamed app was said to record video in a square-shape"), not going to be too optimistic about this attempt either.