To quit your list, all the user need do is click the banner. The click sends an email to you (or your email service provider) that instructs you to remove the user from your list.
Opt-outs have soared since the August release of Version 10.
There is one way to thwart Apple: enable opt-outs only through a website. If your email contains only a URL for unsubscribing, the ginormous unsubscribe banner won't be displayed.
HAT TIP: Thanks to Mike Bannan, CDO of Inspire 360, for bringing this to my attention. Before he mentioned Version 10, I was at a loss to understand the surge in opt-outs.