What does Spotify's new App Store/API mean for them, their competitors, and the online music space?

Spotify announced today their vision for turning the Spotify App into a Platform [for music], a la how Salesforce took CRM data and allowed 3rd parties to build apps that leveraged that data to create new value for customers.

Examples include:
- a Rolling Stone magazine app that will fill the gap of music curation and discovery for Spotify users.
- a Last.fm app which shows your recent Scrobbles, recommended artists, and other content.

As with all the apps on Spotify the biggest benefit here is that the user can click on a song and it will begin playing (assuming Spotify has it in its vast library).

The ramifications of this development are pretty cool in my mind. This has the opportunity to finally close the loop for the consumer. I find good music via numerous sources - I can listen to it right there - I can buy it.

Imagine the entrepreneur that simply wants to create a music curation service. Now, they build their app, focus on their curation content, and don't worry about the music licensing BS.

The tradeoff is, following the Apple paradigm, you're locked into the Spotify App.

So... What does Spotify's new App Store/API mean for them, their competitors, and the online music space? Will we see other music App Stores crop up like we saw with Android after the iPhone app store? What do you think this means for iTunes, Google Music, Rdio, MOG, etc.?