While your intentions are good, the end results are bad. In order to pay the CPA rate on the campaign, the merchant depends on people continuing on through the signup path beyond entering their e-mail address. That won't be possible if they've only got a small iframed window to do it in.
Shouldn't be an issue if I target _blank the submit button. The second page of the signup path will open in a new tab/window. I think I can actually target the parent frame and just have it open in the same page even (not 100% sure about that.)
Additionally, most merchants have to put tons of disclaimers and legalese on their landing page in order to avoid getting in trouble with the FTC. They don't look too kindly on people who frame that out for the convenience of a cleaner landing page.
Hmm, yes I can see that being an issue. I could copy that over as well.
I can see there are issues with it, but at the end of the day the most important thing is still conversions - If I'm bringing in conversions for the merchant, there's usually a lot of leeway to work with. We both want to make money.