It's when I click on unsubscribe link at the bottom of some email message and opens up a Web page asking me to type my email address there. What the fuck? Didn't you just send me this email? Don't you know my email address?
Well, I'm talking about legal email advertisements here. They are not supposed to be delivered to you whatever it takes, crashing everything on the way. I had willfully opt-in for them and now I want to opt-out. So please, tell me, why are you trashing my experience working with you by giving me a feeling of a nasty SPAM-machine? It is wrong.
Guys, whenever you build something, keep in mind that the truth in simplicity. Nobody wants to do your job. Make the user experience one-click. And when it happens, trust me, he'll want to click once more.