Unsubscribing from e-mail newsletters

I thought I'd try my hand at this today and just found:

• It slightly annoying when you are sent an e-mail confirming that you've unsubscribed (hello, I just told you I don't want your e-mails!)
• Even worse, you're asked to log into an account that you never created in the first place. My best guess here is that I registered to some other site owned by the same company. Though their 'password reminder' e-mail still hasn't come through.....