EDIT: The top 10 pop chart artists all seem to have around 100k followers, will be interesting to see how it goes.
iTunes could satisfy the iTunes user market. But unless clusters of friends all use iTunes, a decentralized service will be more useful. And i'm not sure if being an itunes user means more of your friends use itunes (to any level of significancy). So chances are most people will have a bunch of friends who can't participate.
Apple do what they always do.
Not everything that is possible only what is necessary.
Apple have entered the social space, it's official, people will now know.
Then they will improve on it step by step.
It's obvious that the problems with facebook integration is also affecting our perception a great deal.