Some really interesting information on participation in MOOC forums from Stanford Online:

Online discussion forums are seen as an important part of the MOOC experience. One current course lists in its opening announcement

DISCUSSION FORUMS: The discussion forums play a crucial role in massive online courses like this one, which is an all-volunteer effort. If you have trouble understanding a lecture or completing an assignment, you should turn to the forums for help. After you’ve mastered the lectures and assignments for a given week, I hope you’ll contribute to the forums and help out your fellow students. While I won’t have time to carefully monitor the discussion forums, I’ll check in and answer questions whenever I find the time. In previous iterations of this course, students have fostered a fantastic and supportive learning environment.

We wondered if we could learn more about forum usage by looking at the data exports Coursera provides. We didn’t have access to the clickstream data that would tell us about forum views, but had access to data about posts, as well as other data, such as the grades students earned in the course.
Here are some initial exploratory results that we hope will encourage others to dig deeper.

The data: % of students who post

We looked at data from 23 Stanford courses that ran on Coursera between early 2012 and early 2013.
First, we wondered what % of users posted at all. Many courses include an “Introductions” thread or sub-forum, so we also looked at how many students posted more than once, to exclude those who simply introduced themselves. Here’s what we found there:
Forum posters as % of all registered students
Read more.