I'm a big fan of the work in the latest Community contest and I wanted to try making one of my own.

Unfortunately, MailChimp removes any form elements even CSS inlining disabled. I ran a test in Campaign Monitor and while my implementation didn't work for the :checked elements, the form elements are still in the code. I figured other people may want to chime in with their experience with services and their support for form elements.

As an aside, my workaround was to use :hover on divs, but I couldn't leave that in for small screens.

Campaign Monitor - Yes
MailChimp - No