Wow, that wasn't my experience at all. I've actually resigned from their service twice. Once last year and once a few weeks ago. (I decided to give it another try this summer) All I needed to do was go to the account menu in their client app, and choose "change status" from paid to "light" (free). It took about 10 seconds and in an hour or so I got a confirmation email back saying that it was cancelled.

The only two differences I can think of are that I didn't try to cancel the light account (I wasn't that motivated), and I was dealing with napster.ca. I suppose there's also the possibility that they've changed their policies in the last couple of weeks or so.