The problem with adding these to the education section is they are not in the same league as a degree, and they clutter the section, especially if you have many. CVs need to be short and easy to parse. A Coursera course, while substantial, is still more like a single class at university. It shouldn't look equal to a degree in the profile.
A second problem is that people tend to place their education chronologically, with the most advanced (and therefore most recent) degree at the top. Online courses typically happen after formal education in time, but putting them first gives them undue precedence. I'd much rather an employer saw my highest degree than some Coursera course.
For these reasons, I've added my Coursera courses to the 'Certifications' section, even though they are not certifications in the traditional sense.
I believe there should be a separate section for such courses, in the same vein as online articles, and open source repositories.