Easy way to add opt in email list checkbox at checkout??

I would like to have an opt-in button on my billing / shipping pages that defaults to checked so that I can start adding these customers to my mailing list.

Is there an easy solution to this?

Has anyone successfully created this?

Does anyone know if this is possible? I want to add all my purchasing customers to my email list, but I'd like to have a checkbox on that page so that they can opt in?

Not necessarily easy, unless you know MVC.  The right way to do it would be to custom code the M,V,C code.

The hack would be to copy the javascript from the home page (i.e. go to demo, right-click page, view source, search for "subscribe").
The script makes an ajax call.  You could probably modify the html and script so that on form submit it looks at check box and calls ajax if needed.