Since recently you can register again without a facebook account. You just have to scroll down. (https://www.spotify.com/nl/signup/open/)

I would suggest people not in the netherlands not click that link as it sets your language preference and you need to go searching for the language switcher :P

It used to be just email but when Facebook promoted their open graph integration heavily they made it Facebook signups. Probably some deal they made with Facebook.

Every single time Spotify is mentioned in the tech community, this happens....