Here are some of my experiences with the problem-based learning MOOC I attended. This Mooc, considering its subject, was all about collaboration. With respect to working with team members, I noticed that, while our group started with 14 members, only a few actually contributed. We ended up in some fuzzy state with 3 more-or-less active members. For such a Mooc it seems success depends on an active and committed team. There was, however, no way to make sure your team would be like that
The commitment problems showed themselves in many ways, from not putting an effort into understanding the design of Mooc, to not reacting to posts from others, to low quality contributions, and of course going absent-without-so-much-as-a-goodbye.
Some of these issues where perhaps also due to the course design and platform affordances. Group discussion could only take place in one long thread. Creation of documents on which to collaborate was cumbersome.
The design-choice was made to not provide support outside some general course-wide discussion boards.So there were no tutors, no teachers to interact with. Overall, the information about the PBL process and the workings of the system both were lacking in clarity. So if you ask me how it went, I would say: not so well. There was a lot of overhead to cope with.