I like those "you have unsubscribed" emails for another reason beyond what you layed out.
I collect them so that I can keep a record of what I've unsubscribed from, so if I ever get spam from them again I don't have any doubt as to whether or not the sender broke their promise to unsubscribe me. It might just be me, but it is doubly aggravating to get spam and feel like I had previously unsubscribed but not be able to prove it. With proof I can be righteous in my anger and blacklist all future email from them. Without proof I am left to doubt my self and wonder if unsubscribing (again?) would be futile.
I collect them so that I can keep a record of what I've unsubscribed from, so if I ever get spam from them again I don't have any doubt as to whether or not the sender broke their promise to unsubscribe me. It might just be me, but it is doubly aggravating to get spam and feel like I had previously unsubscribed but not be able to prove it. With proof I can be righteous in my anger and blacklist all future email from them. Without proof I am left to doubt my self and wonder if unsubscribing (again?) would be futile.