Interesting post here on Professional Learning Communities versus Personal Learning Networks by Lorraine.
Choice and options are important in networked learning as shared in my post http://suifaijohnmak.wordpress.com/2012/02/14/change11-autonomy-in-networked-learning-and-connectivism/
There are differences between Professional Learning Communities and Personal Learning Networks. Professional Learning Communities are more aligned with the FORMAL COMMUNITY OF PRACTICE, and there may be mandates as to how it would be sponsored, organised, and coordinated, with definite role definitions for community managers (principal, head teachers, counselors etc.) and other community members. Those are rules based COP with definite outcomes, and sometimes could be running under a committee structure.
The PLN are more aligned with the Social Network approach where learning is emergent and thus would allow for more personal autonomy. Previous researches (from our CCK researches) have revealed those observations by Timothy and many other networkers, in their various manifestations of blog postings and forum discussions.
These tensions always relate back to the choice, power and decisions, often associated with communities and networks. The group versus networks discussion throughout the CCKs http://wwwapps.cc.umanitoba.ca/moodle/mod/forum/discuss.php?d=956 would be relevant here.