Spotify has begun implementing video into its streaming music client. It's currently running an advert for the movie "The Taking Of Pelham 123" that invites the user to "click to view the Pelham 123 trailer on the new Spotify video player".
That trailer then opens in a borderless Flash video player inside the app, complete with pause, play, rewind and volume controls. The development provides proof of the concept that Spotify could very easily enable a version of its service that would stream video in the same way that it currently streams audio.
Founder Daniel Ek has said several times that video isn't something that the company's interested in doing yet, but this shows that the technology is ready behind the scenes - it just needs some content. If Microsoft's video streaming service, recently announced, gains traction, then Ek may reconsider his decision.