1. Working simple example
I managed to get that example working. My first attempt had errors due to copy/paste issues from the website with the code. Here is the simple working example using jQuery: http://jsfiddle.net/WWaFQ/3/
2. Example using Slick Ajax Form with jQuery
I decided to have a go at a more complex example of using jQuery to show/hide form fields. I've created this working example which contains one conditional form field that shows/hides itself when you select "Nope" in the answer to the previous question. Check out the live example here: http://jsfiddle.net/r262B/1/
What does all this mean for Contact Form 7?
If you use the "div" method I have applied within my second example above, you could very VERY easily write a .js script to show/hide form fields generated by Contact Form 7...without modifying any of the plugin code at all!
Happy days :)