A lot of customers don't check the Newsletter Subscribe box on signup, and then never consider it ever again.

So if they are unsubscribed and place an order I would like to give them a friendly reminder (Nag them) with a checkbox on the Shipping, Payment and Confirmation pages, to subscribe.
If they do, then I want the checkboxes on following pages to not appear.

I am just wondering if some one has done something similar to this?