It'd be nice to be able to Face tweet plus messages to a Google+ pages account. From what I gather they haven't made this open yet, but they did at least allow some early developers: http://mashable.com/2011/11/15/google-plus-pages-third-party-apps/
Hopefully you guys can pull some strings and get access for NationBuilders as well!
The Chrome spellcheck doesn't work in the WYSIWYG for likely technical reasons, but it's a pain to have to alway use an external editor in order to make sure that simple spelling mistakes aren't present. Hopefully some kind of solution can be developed.
For any other payment or sign up page, I can’t think of a single example for the single field. I think you guys need to seriously consider what users are asking for here. You can make it an either or option if you really believe that more issues are created from the multiple field option, but personally the single field is the only thing creating problems for me.