Because i use an iphone, when I have my spotify premium account logged in (using my old facebook account stil, because of your attitude towards facilitating account switching) I cannot use the facebook app with my new account logged into it because the iphone will only allow one facebook account to be signed it at a time. So according to your policy, when i create my new facebook, i cannot merge or switch my subscription to this new facebook account. For example, I personally had to create a new facebook account for personal use, aside from my original facebok account, because there was a recurring error where no other users could post on my wall.
I know many people at spotify would love/like/hate Mark Zuckerberg and his team at facebook, so It may come as a surprise to some that the facebook system has some flaws and anomalies. Im surprised that an organisation as revolutionary as spotify could be so dogmatic and bogged down in this area.