That's a good point and this would be one of the extreme examples of a client who had lists that changed all the time. With Aweber I know you can move people to a different lists from doing certain actions off another list like unsub and sub but if you import just the email they would have to opt in again. So, I could see peeps getting pissed if you are offering better value to potential customers. I guess I would just do one general special for everyone unless you run some kind of "specail deal" a couple times a year.