I think Spotify has attained a customer volume that would allow them to continue to work towards the option of total independence from other social media. Users coule either continue to keep their spotify hooked up with their facebook accounts for ease of access and consolidation, or they could opt to have their accounts seperated.
A facebookless account ought to:
In summary: an independent spotify would act much like it's own social media platform. It wouldn't require users to maintain their facebook accounts or aquire one in order to use Spotify Social, but if some find it easier or preferable they still have the option of using facebook as their method of using Spotify. This would free Spotify from the handicap of requiring users to subscribe to a third party in order to user the Spotify system, but still allow them to do so when it is convenient.