It used to require a facebook account initially (at least here in Germany, right after the launch). I had to create a one in order to open a Spotify account. The option to register using an e-mail address was added later and I migrated my account when this was done.
Are you sure it required one? It may have made it very easy to sign up with FB and very hard to sign up with email, but email has always been an option (in the U.S.)
Email sign up has been possible in New Zealand for a long time, years I think - billing is though Australia so I suspect we hang off them somehow. I haven't got a Facebook account.
edit: I live in the U.S.