Marketing managers don't want to learn some type of special markdown, and I can't imagine they would ever prefer it to a nice WYSIWYG form creator like Wufoo or SurveyMonkey.
No one wants to try and figure out exactly where to click and put their "X" for each choice - that's a much more frustrating user experience than native form controls, even in a desktop browser. On a mobile device? Forget it, and don't forget that something like 30% of emails are opened and clicked on mobile devices.
Apparently Google Forms has a way of embedding native forms in emails, although I'm not sure how they do it:
http://www.gettingmoreawesome.com/2011/05/24/increase-survey...
Now that would actually improve response rates, and was what I was hoping to see here.