Does the link unsubscribe instantly, or must the user log in bla bla bla .. More often than not, I find following those unsubscribe links very annoying because

Does the link unsubscribe instantly, or must the user log in bla bla bla .. More often than not, I find following those unsubscribe links very annoying because I have to log in and fill out 5 different forms.. and then it doesn't even work :(