ACCOUNT DELETION
If you wish to close your Spotify account, in order for us to easily confirm that you are the owner of the account and your wish to close it, please do the following:
Log in to your Spotify account profile page on the website
Under "Personal information", edit your email address to add ".del" to the end of the address
Example: anne@example.com would become anne@example.com.del
Click "Save profile"
Your account will then be closed within 48 hours.
Kind Regards,
Anne H
Customer Service Advisor
Spotify Support Team
http://www.spotify.com/help
This the reply email I received from Spotify Help and Support in regards to closing your Spotify account.