You've nailed it. All the things that make Apple's business model advantageous – the meticulous scripting, the secrecy, the glossed-over experience – work wonders on hardware. But when it comes to social networks, it's clear that they just don't understand the model at all. Because they can't do ANY of these things and have a successful social network.

This was roughly my thought too. A social network that will only ever be available to a small niche (iTunes users that purchase music on the ITMS) is hardly social. Last.fm is available to anyone regardless of their platform or where they got their music, with the obvious caveat that they need a plugin for their music player.