Hello everyone. I am just parachuting into this conversation, which I realize could be rude as I've only skimmed a few posts. But I care deeply about this topic, thought I would toss a few ideas into the pot and apologize if they have already been explored. (How Canadian is that!)
For over a decade I've been interested in--and working with--different ways of looking at leadership in different contexts, including highly collaborative contexts. A few of us have been on this somewhat lonely path for a while; some are much more published and involved in more regular academic research than i am (Mary Uhl-Bien being one example).
There are so many ways of thinking about leadership (and related theories). Manager=leader (I fight that one); top-down leadership (love being self-employed), servant leadership, leadership from the side, distributed leadership and leadership as an emergent property. Many of the collaborative environments I've been watching could be characterized either as having distributed leadership (I use the term fairly generally; not necessarily exactly the way Gronn does) which regularly shifts, or as having emergent leadership, which one might not even associate with people as entities (using complexity language).
Hope that is food for thought for some community members!