I often advise people to create a dialog as part of the unsubscribe process. Typically, the topics are
1. Frequency Reduction. Ask people if they really want to leave, or if they just want less mail.
2. Survey. Ask them why they are leaving, so that you can get better.
ProFlowers (not someone I've worked with) got it all wrong in my opinion.
I clicked the unsubscribe link. They presented a survey. I was busy, so I didn't feel like answering and just wanted to unsubscribe. But they wouldn't let me. It was early in the morning, and so it took me a while to figure out that unless I answered one of their questions I could never get off their list. It annoyed me and I'm sure it annoys others.
It would be interesting to have a legal perspective on whether this meets the letter of the law and the spirit of the law for CAN-SPAM.