I commented on what this might mean in . One vital piece of information missing at the time was that, in at least one case we now know of, Facebook membership is a requirement to belong to the service. That service is .

According to a Spotify representative: "New accounts require Facebook to log in and this is a worldwide initiative. To us, this is all about creating an amazing new world of music discovery. To make this as good and simple as it possibly can be, we've integrated Spotify login with Facebook login. By adopting Facebook's login, we've created a simple and seamless social experience. Once a user is logged in they can control what to share to each of their networks from the preferences menu in Spotify."

I've checked in with some of the other music services, and both Mog and Rhapsody tell me that while they're participating in Facebook's music service, they are not exclusive to it. You can have a Mog or Rhapsody account without also having a Facebook account. Each of these services additionally offer its own social networking service.

Putting aside the issue of whether this really is about "creating an amazing new world of music discovery" or the more likely matter of Spotify increasing its revenue thanks to better placement and a piece of the action, it very definitely puts Facebook in an important place in the music business. It's now a significant music distributor and in the position to make demands of music companies as well as promote particular labels, artists, and publishers to millions of Facebook users.