I've been unsubscribing from some junk email recently.
The user story is simple: As a not-very-interested person, I want to get off your dumb-ass mailing list so that I don't have to flag your crap as spam any more.
The implementations vary from good to evil. Here's what I've found.
The best sites have an unsubscribe link that simply presents the facts -- you are unsubscribed. I almost feel like re-subscribing to a site that handles this use case so well.
The first level of crap is a site which forces me to click an OK or Unsubscribe button to confirm that I really want to unsubscribe and wasn't clicking the tiny little links at the end of the message randomly.
The deeper level of "marketing" crap is a form that allows me to "configure my subscription settings". This is done by some marketing genius who wanted to "offer additional value" rather than simply do what I asked. This is a hateful (but not yet evil) practice. I don't want to "configure" my settings. I want out.
The third-from-worst is a form in which I must enter my email address. What? I have several email aliases that redirect to a common mailbox. I have to -- what? -- guess which of the aliases was used? This is pernicious because I can make a spelling mistake and they can continue to send me dunning email. This fill-in-the-blanks unsubscribe is simply evil because it gives them plausible deniability when the continue to send me email. It's now my fault that I didn't spell my name correctly.
The next-to-worst is a "mailto:" link that jumps into my emailer. I have to -- what? -- fill in the magic word "Complete" somewhere? You're kidding, right? This is so 1980's-vintage listserv that I'm hoping these companies can be sued because they failed to actually unsubscribe folks. Again, this gives the spammer a legitimate excuse because I failed to do the arcane step properly.
The worst is no link at all. Just instructions explaining that an email must be send with the magic word "Complete" or "Unsubscribe" in the subject or body. Because I use aliases, this will probably not unsubscribe anything useful, but will only unsubscribe my outbound email address. This is the worst kind of evil. In a way, it meets the user story. But only in a very, very oblique way.