DISQUS

I've seen this before and quite frankly don't see any success Myspace is going to have on this venture. They do excellent in promoting artist concerts/shows and new music but other than that i don't forsee there popularity growing in the same term as iTunes.

The one thing that could hinder this that I know personally working with a lot of artist using myspace as their main "website" use 3rd party extensions to sell their music and/or merchandise.

Its just another lame attempt as another company decides to go towards the social networking road. The best bet is to join up on the most popular ones such as the ones you mentioned (FB and MySpace) and publicize their presence on there.