Spotify has just introduced its new “Play Button,” a customizable widget that users can embed on any site, just like a YouTube video. Awesomely, the widgets can stream entire albums or created playlists, in addition to the standard single track.
Smaller services such as Soundcloud and Mixcloud have had similar capabilities for some time, but Spotify offers an immensely larger song library. However, the main drawback here is that Spotify has limited playback to only registered users, and the “Play Button” requires the service to already be open on a user’s desktop prior to clicking.
All in all, it's a decent start on the road to open streaming.