In fact, this is just an addition to the option which was already in the Spotify client which already allowed users to turn off sharing via Facebook entirely.
Just 3 days earlier Ek tweeted that the company listens to criticism and makes changes accordingly. But today's announcement is still dismissive of the people who simply don't want a Facebook account.
For some the reason is a general distrust of Facebook, while others simply don't see any benefit to it. But just as importantly, many people don't want to be given an ultimatum telling them to sign up for a third party service whether they want it or not.
Ironically, Spotify's success has been predicated on choice. It allows you to choose not to pay for your music without breaking the law.
Requiring a Facebook account probably doesn't affect too many potential subscribers. The negative publicity may be another story.